I recently had a conversation with our DM about us players feeling it was both immersion-breaking and less fun that the DM plays all the monsters with optimized, coordinated tactics, even if the monsters are reckless or stupid, and often leveraging knowledge about our abilities the monsters do not have.
The DM in response complained that it's no fun for them having the monsters be defeated all the time, without posing a real challenge to us, or taking anyone down once in a while. 1
I can empathize. I used to be the DM for our group for about a decade. As a DM, you may be all-powerful and godlike in what you can present to the players, but in the end, the game should be fun and in my experience players rarely feel being overmatched, powerless, or TPKd is much fun.2 Even being bailed out isn't.3
So your job as the DM is to have the guys you run lose, pretty much every time. Because if you don't: end of campaign, or at least major demoralization event. And, with time, this can get to you. You begin to want to make some dent into those player character HPs. Sure, you should be an impartial referee, but it can be hard to remain neutral or a fan of the PCs, when you are the one running the monsters. It can be hard to not start identifying to them as "your" team. At least that was my experience, and I had to consciously remind myself to not fall into that trap. Our current DM seems to struggle with the same things.
What self-talk, or what line of thinking that we might be able to share with our DM has helped you or worked for you to overcome this kind of side-taking or DM fatigue? I am looking for good-subjective, practical experience based advice.
PS: There is the similarly worded question "How do I deal with DM burnout", but that seems to be focused on the DM just in general having too much on their plate and getting tired of associated real-world hassles like scheduling, hosting, cleaning up afterwards etc. Here, I am concerned with dealing the psychological challenges of continued DMing.
I tagged this with D&D 5e, as the mechanics of D&D have some impact here, but a general answer that is not specific to 5e would also be welcome. I think earlier editions had similar issues.
1 D&D 5e unfortunately does not have supportive mechanics for player characters or monsters aborting a losing fight. The movement rules are not much help, attacks of opportunity make it hard to get away and put in enough distance. And while each group of monsters is only in one fight, for the PCs all losing any single one can mean end of the campaign. So it is risky to put on encounters that are deadly in the actual sense of the word too often -- sooner or later one of them will go the other way.
2 Your mileage may vary of course, there are many playstyles. Maybe you have a group that loves old-school hard knocks. Mine expects to be able to make it with good thinking and care, or at least have some kind of warning signs that we are in over our heads.
3 Our DM has begun to increasingly take those risks, with fights that are 5-10 times the XP budget of a "deadly" encounter. One already did, and then the DM had to shore it up with an uber-powerful NPC stepping in to save our hides. But having to be bailed out this way by DM mercy in response to the DM mis-estimating their guns and slaughtering us feels unsatisfying on both ends, because it means your actions cannot really make a difference, you are just a stooge in the DMs narrative of powerful forces clashing.