Indirectly

With some GM's, and/or in some groups, working through the indirect line may be better to deal with problems like this. As you've stated in your question, the group has a habit of rotating GMs. And this is just the time that the person GMing now is not what you're looking for. Maybe you should look for an indirect solution.

Sit as a group and define what the GM's role is

Take a break from the campaign, or wait till it is finished or something, and sit as a group to define what the GM's role is and what the players' role is. It is extremely important to know, to have a hard definition of what one should do in the game. Both of those roles, players and GM alike, are far less defined than we would expect and it leads to many problems of authority allocations. Sit and talk about it. Is the GM's role in your games to be the only storyteller? Does it lean to a more equal-weight kind of storytelling, with the GMing having the ability to veto? Through this conversation, many of your problems will surface naturally, and all of you will leave with many things to think about. The thoughts that will run in your heads will lead you to better games, games that are far more suited to your likings.

Suggest reading-material

If you have a tendency of GM-rotation, bringing reading-material for the entire group, like articles or GMing books won't seem that much as a critique. Present it as your latest finding and he will take it much more lightly. The reading material that you should present to the group should deal, at least to a certain degree, with the problems that aroused in the game.

Go together to an improv seminar

Improv is a really nice skill to improve, and it is useful to the entire group. It can help to roleplay the characters better, to think about ways to improve the story from both roles (GM's and players', respectively) and so much more. If you don't have an improve class near you, there are some lectures and presentations all around the net. Articles are great also. I saw once a really nice presentation in TED that showed the difference between a story that is being told with "yes"s and a story being told with "no"s. It is amazing to see the difference.

Directly

But maybe you need to go through the other route, maybe because the indirect line failed you, or because you don't think it will work for one reason or the other. For that, we have the direct route.

Go to your GM and just speak with him about it. Whether it is before the session or after it, sit and talk with him. It is usually advisable to have the conversation after the session, as you can give examples from the session that just took place. Tell him about your problems, about why you stopped enjoying the game, and suggest some solutions that might work. Then, together try to figure a solution that will bring back the spark of the campaign.

Leave the game, the campaign, for a short while. While this person is behind the screen, don't come to the session. Sooner or later, questions will be raised and a conversation will embark. Then resolve as appropriate.

Maybe you will just have to compromise. Suggest this to your GM, and if he agrees, both of you will compromise a little in order to have a better game. It will be a little bit harder at first, but if you will fill your part he will have to fill his. The game will be far more enjoyable for you. After all, he is not necessarily a bad GM; he just has a different play style.

If you are not alone in this, maybe just switching the GM, or even the entire game, is better for all. Present it nicely, and explain that it is not personal, but just that the time has come for this switch. If he asks, explain calmly why you are all for the switching.

Indirectly

With some GMs, and/or in some groups, approaching the problem indirectly may work better. As you've stated, the group has rotating GMs and the problem is only that the person GMing now is not what you're looking for. This suggests looking for an indirect solution might be good.

Sit down as a group and define what the GM's role is

Take a break from the campaign, or wait 'til it is finished or something, and sit down as a group to define what the GM's role is and what the players' role is. It is extremely important to know in order to have a hard definition of what one should do in the game. Both of those roles, players and GM alike, are far less defined than we would expect and it leads to many problems of authority allocation. Sit and talk about it. Is the GM's role in your games to be the only storyteller? Does it lean to a more equal-weight kind of storytelling, with the GM having the ability to veto? Through this conversation, many of your problems will surface naturally, and all of you will leave with many things to think about. The thoughts that will run in your heads will lead to better games, games that are far more suited to your tastes.

Suggest reading material

If you have a policy of GM-rotation, bringing reading material like GMing articles or books for the entire group won't seem that much like criticism. Present it as your latest finding and he will take it much more lightly. The reading material that you should present to the group should deal, at least to a certain degree, with the problems that arise in the game.

Attend an improv seminar together

Improv is a really nice skill to develop, and it is useful to the entire group. It can help you roleplay characters better, to think about ways to improve the story from both roles (GM's and players'), and so much more. If an improv class isn't offered near you, there are some online lectures and presentations. Articles are great also. I saw once a really nice TED Talk presentation that showed the difference between a story that is being told with "yeses" and a story being told with "nos". It is amazing to see the difference.

Directly

But maybe you need to go the other route, maybe because the indirect approach failed, or because you don't think it will work for one reason or the other. For that, we have the direct route.

Go to your GM and just speak with him about it. Whether it is before the session or after it, sit and talk with him. It is usually advisable to have the conversation after the session, as you can give examples from the session that just took place. Tell him about your problems, about why you have stopped enjoying the game, and suggest some solutions that might work. Then, together try to figure out a solution that will bring back the spark of the campaign.

Leave the game, the campaign, for a short while. While this person is behind the screen, don't come to sessions. Sooner or later, questions will be raised and a conversation will ensue. Then resolve as appropriate.

Maybe you will just have to compromise. Suggest this to your GM, and if he agrees, both of you agree to compromise a little in order to have a better game. It will be a little bit harder at first, but if you do your part he will be obliged to do his. The game will be far more enjoyable for you. After all, he is not necessarily a bad GM; he just has a different play style.

If you are not alone in this, maybe just switching GMs, or even the entire game, is better for all. Present it nicely, and explain that it is not personal, but just that the time has come for this switch. If he asks, explain calmly why you are all for the switching.