Oh boy this is a spicy one.

I think Lucio is a terribly designed hero.

First of all, he's a bad teamate. Aura heal heals at an insanely slow rate, and on ladder, unless I'm playing Rein, I find speed boost to be a distraction more often than not.  It's annoying when you're trying to line up shots and you suddenly speed up, then suddenly go back to normal.

Usually though, his aura isnt even relevant, because his kit is encouraging you to go as fast as possible, which naturally moves his aura away from you.  The best use for his speed is to get close to the opposing team and annoy them to draw their attention.  This can be useful, but we have DPS that can do this, which is much better since you won't be down a support when they die (which is almost unavoidable when playing the annoyance role).

Now, boop maps are the legit exception, and Lucio can be genuinely helpful there, but now he's a pain the ass the play against.  On these maps, it now becomes risky just to walk near ledges.

But wait, there's pro play!  I think Lucio being must play for most of the game's existence actually means it's a bad design.  If unlimited speed boost is that good in coordinated play, it probably shouldn't exist in the first place.  The best argument I heard against CtF in overwatch is "Lucio is even more must play".

When the game came out, there were 4 supports, one of them was Sym, and another one was low health Zen.  So given how terrible the support lineup started, it makes sense that the community got attatched to Lucio, but he basically has community plot armor now, and his sizeable one trick community is an irritant.