The crossbow has been in the game for a long time and it seems like only recently have people started to have a problem with it. The combination of it building uber % + the movespeed buff I think is what led to a lot of frustrations people have with it (and arrow building but people just took awhile to understand how broken that was). I haven't played this game seriously in quite a while so I don't have any scrim experience with it, but from the sporadic pug and observation of streams the game appears to play much faster. Especially in team fights. Medic is more durable and soldier can jump around to distract then get back to his team to get arrowed, then re-aggress. This playstyle leads to more situations in which you have to arrow people who are standing still, because people are playing around the expectation of getting arrowed.
So if the game plays noticeably differently, is that necessarily a bad thing? If the crossbow is changed to no longer build uber, it would just stop arrow building (which is pretty retarded imo), but the whole "3 people standing around the medic waiting to get arrowed thing" would still happen. And the speed of team fights would stay at its accelerated pace.
So say you ban the crossbow, do these situations that people don't enjoy change into something more "fun"? I really don't think so. If your biggest gripe with the crossbow is that you have to sit there and arrow people 5 times in a row I really don't understand what you want from that situation to make it more "fun". You have to think about what an unlock adds to the game, and what the game becomes with the absence of that unlock. The people who are currently playing at the highest level are overwhelming in support of keeping the crossbow (am I wrong in this?). Overall the net benefit of the crossbow being in the game outweighs the negatives it brings and I don't think it should be banned (uber building needs to go though for real).