Not in 5th Edition. In 3 and 4 e, when Feats were smaller in individual impact and gained every other level, stuff like that was great. But in 5th Edition, Feat choice has a lot more gravity to it. Most games you can only really count on seeing 2 ASI levels, maybe 3 if you’re playing a fighter or a rogue, or the game goes to 12th level. Which means only 2-4 Feats at most in a typical character’s career, and they come at the opportunity cost of a potential +2 to an Ability Score. Those Feats each need to be a huge deal to be worthwhile. A Feat that enhances a Class feature would have a very fine line to walk between not feeling worth it over a Feat that will let you do something new, and feeling so good it’s effectively a tax for characters of that Class.
Yes it is
Sharpshooter is definitely not what I would want as a basis because it makes you straight better at a huge area, since it's probably going to be used all the time.
Another bad example would be a feat that lets a Druid cast in wildshape. That is totally going to be a must have for druids.
So they would have to be feats that:
- do not remove or bypass a fundamental limitation of a class ability
- do not give a straight "vertical" boost to something that is used all the time
- do not just increase how many times you can use a special ability (although a small increase might be ok)
- may grant more options to choose from when using an ability ("horizontal" benefit)
- may grant some modifications or additions when using the ability, but in a way that doesn't feel essential ("diagonal" benefit)
For example, some of the Rage extensions of the Berserker could have been feats. None of them is so essential that makes other Barbarian subclasses feel cheated. But now I wouldn't want feats for these because there is already the Berserker, I am just quoting them as an example.
Another possible direction would be the plain horizontal. For example a feat that lets a Sorcerer pick a couple of extra Metamagic effects, or a Monk of the Four Elements pick more special elemental abilities, or a Cleric gain a new Channel Divinity effect. You're still bound by all the normal limitations including number of uses.
Would these still feel like a tax to you? IMO a player may be totally fine with having her basic number of effects available and would feel that these are really non-essential.