Well, that is Malzahar for you, he is reliable in that he can hold the mid lane against most comps, and he punishes people who try to all-in like Yasuo and Fizz. People's issue with him is that you can't tower-dive him without screwing yourself over, in which case he is no different from Morgana. That issue is a low-elo mentality where everyone wants to be a LoL hero, and get the sickest kills. The issue is that he can't burst you 100-0 unless he can get at least his suppression on top of his pool, in which case it's your fault usually for being so close to him... it's not like he has any sort of mobility beyond... well, floating.
He sort of functions like an anti-assassin assassin, in that he will focus the guy who tries to get in and kill your squishy members, but after that he doesn't contribute much to a teamfight beyond a bit of poke and maybe some zoning with his pool, unless he can land that silence. However, he has very lengthy cooldowns even with CDR, which is what limits him in a teamfight beyond locking down one person and then being reduced to less than reliable pokes. He's not broken because he has clear limitations and he only functions as an effective duelist, and the issue is that duelists are either very good in teamfights or very bad at teamfights, and Malzahar falls into the latter.
Simply put, people who play Malzahar like to play safe and conservatively, they only move to kill on their terms, as long as you don't give them the chance, it just becomes a farm lane.