The problem with the crossbow is that the "flow" of the game has been changed by it too greatly.
The original design intention, in tf2, since the beta when kritz heals were introduced, was that players would engage each other, and then either commit fully to dying for frags and be penalized by a respawn timer, or back up to be healed by their medic. The players who backed up and took a breather would be rewarded for this behavior by receiving more, and faster, heals and not be penalized by a respawn timer.
When you introduce the crossbow you ruin that whole arrangement due to the amount of healing it puts out, and the way in which arrows are typically dealt with (hiding behind props somewhere while standing still). It allows for you to re-enter fights much more quickly and also doesn't force you to collapse around your own medic (or health packs) for healing. So you end up with mid-fights that last longer, and scenarios where pushing off of damage alone are much more difficult.
Let me take you back to a time when you could peek badlands choke, and if you hit 2 solid rockets on the other team's pocket or demo (who would be spamming like a dummy from that choke) you could push regardless of the situation because you knew it was going to be at least 10 seconds before that guy could ever do anything productive without risking his life. Now he just stops moving and takes an arrow and all is well. The same occurs frequently with heavies on lasts. The old scenario far more interesting than the current situation where teams never to very rarely push off of somebody just getting hurt badly..
It's not rose colored glasses - it's objectively superior. Damage actually means something, and the game naturally flows between engagement and reorganization, and retreating is part of a wider and deeper thought process than finding a spot to stand still to take an arrow right quick. Preserving the game's flow is why kritz-heals were introduced all those years ago, and for some reason they decided to throw it out the window in a bid to give medic something else to do.