I would agree with that...-5 is a significant penalty. We had a player who played with our group for a couple of sessions and he had the sharpshooter feat, and he used the -5 option all the time trying to do massive amounts of damage. At the level they were at, I think his to hit bonus was +8. So he was taking over a 50% attack bonus cut.
I remember watching so many of his rolls fall into that 5 point differential, and they would have been hits, but instead were misses. Those moments were brutal.
For some, it's better to have a strong chance to do 12 damage rather than a slim chance to do 22. I'm no math whiz, but over time, the numbers are probably not as different as we might think.
I find those feats most useful when an enemy is shown to be easy to hit because it has low AC, or for when you have advantage on attacks. But under normal circumstances against a foe with a medium AC IT's risky, and against a strong AC it's bordering on foolish.
I think that the accuracy factor seems to be a bit overlooked. -5 is a big penalty.
GWM and Sharpshooter have been discussed at length. The problem with both feats comes online at higher levels when fully buffed due to Bounded Accuracy. At low level they are generally fine.