All I can say is that I can see some people getting upset if they invested in a feat and it doesn't work as written.
I get it. A feat is a big investment. I just want flexibility of how to adjudicate the action and the intent. Some people will be OK with the target having a different response than what is written, others will get pissed.
Some of these feats feel like 4E powers. I found that while 4E had good points, most people I played with (that had played other versions as well) felt that by having hard coded things like this that it sucked the spontaneity out of the game.
It's a subtle thing, and not something I expected when I started playing 4E. I just don't want to go down the same road with 5E.
It's not that it's not working as designed; it's that it's not working in a way against a
specific opponent, wherein if it was allowed to work would upset others players' sense of verisimilitude. The dude can terrorize goblins and force random thugs to back down all the live long day. I'd start applying circumstance bonuses (that is, advantage and disadvantage) against humanoid foes that are trained to overcome their fear of others (professional soldiers and the like). But against that one big scary dude who knows you're way beneath him? The guy with the authority and confidence to be a legitimate campaign Big Bad? No way it's going to work so why would I bother rolling in the first place? This is not breaking anything, not taking a guy's feat away, and any internal consistency in your world remains absolutely intact.
If somebody actually gets upset because they think they're playing 4e, it's incumbent on the DM to remind them that they are not actually playing 4e.
Now, I'm with you the way in which codifying abilities can sometimes limit creativity and spontaneity in player action, which is why I think this UA's Performer feat is absolutely rubbish (among others). Menacing gives a specific cost in the action economy to the move, which informs me that any player can attempt the same thing, but at a greater cost (a full action rather than a single attack, in this case, or maybe I'm a lot harsher in ascribing circumstance bonuses/penalties to those without the feat). So I can excuse that.
But I also think that, as long as I'm clear enough to my players that just because you don't have the feat doesn't mean you can't ever attempt to perform these actions, but there will be a greater cost or degree of difficulty to them, the existence of these feats will actually
increase the range of spontaneity and creativity in my players. YMMV, but my players would definitely read this and think "I don't even realize I could try to do something like this with [insert skill here]".
Then they'd try to think of other interesting actions that could utilize their skill proficiencies. It could border on silly at times but ultimately I see this is a pretty big boon for my table.