I disagree that the choices are comparable.
Taking PAM/GWM is, if not truly optimal, a first order optimal build. 9 times out of 10 it (or its brother SS/XBE) is probably the correct decision if you're building a straight fighter for damage. It's clearly presented as something the game thinks is a good choice.
GWM/PAM is almost never an "optimal" build choice in a real campaign. Spending two of your very limited feats on that is one of the worst choices available unless you know for a fact you will be able to get a magic polearm that will be able to keep up with the other magic weapons available. Even in that case you are giving up a lot to get it, accepting worse saving throws, worse skills and potential spells for what is a marginal improvement in damage compared to other options available without a feat.
SS/XBE is much better (especially the sharpshooter part of that). I think it is debatable if XBE is a good add on considering the range hit with a hand crossbow and the other feats available, including control options to use your bonus action, combat-related half feats and feats to boost your damage. Sharpshooter alone though is far better than GWM/PAM are combined. It eliminates cover and disadvantage from long range which really improves your capability as a ranged fighter and it makes a Sharpshooter martial the most powerful damage build in the game.
It would be like putting that same trap in the middle of a crowded tavern and then blaming the player for not checking traps.
That is not blaming the player and players die from things that happen in Taverns too.
Let me put a different question in here - If my fighter takes the Mage Slayer feat do I as DM have to make sure there are lots of enemy casters for her to attack? If she has a 9 Charisma\ and takes Shadow Touched with Cause Fear to boost it to 10 do I need to make sure he comes up against enemies with very poor Wisdom saves so she can land that spell often when she casts it? Or maybe I need to give her an amulet or something that makes her Charisma 16 so that spell is effective?
Each of these are poor feat choices, similar to GWM/PAM.
Even then, I said the issue is with the core rules itself - they IMO should allow players to change feats*, in the same way that Tashas now allows you to change out of fighting styles.Though presumably before Tashas you thought that people who didn't choose the "correct" fighting style at lv1 should be doomed to use it for the rest of the campaign.
I am not against this and I have allowed a player to change a feat she chose at 4th level when she got to 5th level.
The PC was playing a Rogue for the first time and Chose defensive duelist at 4th level and used it a lot. At 5th level when she was writing her new abilities she realized it conflicted with Uncanny Dodge. She asked to change because she did not realize it and I let her.
That would be a house rule (I think) , but one that I would support and it is a lot better than catering and prepping specific treasure to make a characters foolish choices less foolisj.