Floyd doesn't have irritated vocals! Specially compared to Plant, Ozzy or Rush. But I can see why people may not dig them, same with Zeppelin, vocals aside.
Someone doesn't have to like every popular or even "great" band. I know plenty of people that don't like the Beatles for example. Reasons I'll respect are, "I just don't get them." "I don't see what the big deal is," or "I understand how influencial they are and how important they are to musical history, but just not my style." Reasons I don't respect. "They suck."
I'm sorry, if they ACTUALLY sucked they would not have gotten that big. Bubble gum pop comes and goes and is forgotten, but ACTUAL bands endure. Nobody cares about the New Kids on the Block or Backstreet Boys anymore, but Pink Floyd lives on even over 30 years after their classic line-up. A bad that "sucks," doesn't do that.