It's always been this way
And it sort of needs to be; otherwise there is no point in character abilities!
In 5e, if my Paladin wanted to "hit someone in the legs to trip them" with his glaive, well, I'm not able to do that, unless I pick up some Battlemaster Fighter Maneuvers through a feat, multiclass, fighting style, etc. In 5e, if I wanted say that my Eldritch Knight, with her opportunity attack, casts Booming Blade, but I don't have the Warcaster feat... well, I can't do that.
For a lot of cases, we have Aid in PF2e (as Matthew Wells wisely pointed out). This would include the feinting for your friend case, but I would argue that flanking already covers that concept (and gives flat-footed).
But, in basically every RPG ever, there has always been limitations to a characters abilities. This allows for characters to gain these abilities, uniquely distinguishing them from other characters and giving them a since of progression and growth.
Taking the slippery slope all the way to its end, an argument that "things shouldn't be constricted by feats" is an argument that "nothing should be constricted", so everyone should have the abilities of every class at 20th level. But that's not fun, because that doesn't create unique characters.
I've had a few similar occasions with my rogue player in my campaign. My rogue wanted to basically muffle an enemy and kill them (the enemy was not unconscious or anything, just not suspecting the rogue to be hostile). I made a quick ruling in session (it was awhile ago, I think I called for a Grapple check, but said if she managed to succeed at that and take him out by the end of the round I'd say she did so silently - She didn't succeed). However, I then followed up with the player this way:
- I apologized to her: "You know, I wasn't a big fan of that ruling in the end, and I want to come up with a solution that works better for both of us." (I did it in front of all the players; I think it is important that the players see that the GM really does care about player opinion, and really does care about a fun game for everyone)
- I proposed a solution: "I think this would be best represented by the addition of some skill feats; I think it is too specialized an ability that just anyone should be able to do it, but I think its niche enough that it doesn't need to be a class feat or feature." (in your case, you could propose Aid, or your could homebrew something along those lines)
- I got the player's thoughts: In this case, she liked the skill feats I had made, and Rogues have oodles of skill feats, so she said "yep, that works for me."
This worked out very well for my group! Note that the "solution" doesn't have to be homebrewing new mechanics every time - reflavoring existing mechanics is often easier (Using Aid for a distracting feint is exactly this)!
The Problem isn't the Problem
Now, you say in your answer:
I recently migrated a 5e campaign across to PF2e. One player has been resistant to this move. As an example,
If I'm reading this correctly, it doesn't sound like your player wants to like Pathfinder 2e. So they won't. You can answer this objection, and they probably still won't like the game. I can't speak for what kind of player they were when playing 5e, but I'd recommend approaching them (personally/privately) and asking something along the lines of: "Hello friend! Correct me if I'm wrong, but I get the impression that you might not be the biggest fan of Pathfinder 2e. It seems to me that the rest of the players (and myself) enjoy this system, perhaps even more so than 5e, but I want you to be able to have fun too! Is this a correct assessment? Can it be fixed short of switching systems back to 5e?"
There's a very real chance that your player says that it cannot be fixed short of switching back to 5e. At that point, you really only have 'tough love' responses, such as: "Hmm. Well, for the sake of the group and myself, switching back to 5e isn't an option. Perhaps we can both try really hard to approach next session with an open mind, seeing the virtues of different systems with different philosophies?"
If the player simply ruins the fun for everyone else and shows no signs of repentance, you may have to ask them to leave the group. This question and answer may be helpful then.