One Piece will be legendary in fiction because of various factors like its anachronistic features, it's nature as a point of pride for Japan, its existence as a genuine feat of world creation, and various other factors (like the insane amount of physical media left over and die hard fans).
If it sticks the landing the flaws can and will be overlooked just like many classical stories have for centuries now. It won't be as insanely popular is it is right now, but a series this impactful won't be forgotten for at least a generation. This isn't Domestic Girlfriend, Chainsawman, or the 9 millionth isekai story cynically churned out.
Luffy is that island nations Superman, and the fact a bunch of normies from America watch the show despite no interest in any other series, means quite a lot. One Piece is good, nothing is perfect and if you really truly no longer enjoy the series, stop being the idiot that falls for the sunken cost fallacy. Move on to "better" series, and just pop back when Oda finally wraps things up in a decade.