I've kept plecos and was very pleased with them. Like most things in life they aren't appropriate for everyone, much in the same way as many other fish are inappropriate.
From my experience, if you want something unusual, interesting, and fascinating with the way it looks, moves, eats, lives, I think the pleco is ideal. If you want something easy to keep that swims around like most fish, not so good. Neither is right or wrong, but some things obviously appeal to some people more that others. For me strange and unusual is appealing. Difficult is just not a major concern.
The poop issues I think are over blown (mind you I fed mine nothing but tons of greens, so poop was super abundant.) For me a fish tank is an opportunity to take a glimpse into a nature. But I'm not bothered if the tank lacks a pristine, sterile, white sandy bottom.