I don't see how loading matters in any way. Crossbows are nothing special even if you don't have to load them.
Crossbow, hand 1D6
Crossbow, heavy 1D10 (two handed)
Crossbow, light 1D8 (two handed)
I mean what is so special about crossbows that makes them OP if you take the loading action away???
Because it makes Shortbows (1d6 damage) and Longbows (1d8 damage) pointless. With loading, if you have an Extra Attack, then you need to decide whether to make one attack with a crossbow at 1d8/1d10 or two attacks with a regular bow at 1d6/1d8 (unless you have the Crowsbow Expert Feat). Without loading, there is no point in using a regular bow, unless it has some special ability you want to use. Crossbows still have a point in 5e, because if you don't have an Extra Attack, then they do more damage, and if you're willing to take the Crossbow Expert feat, you can do more damage AND use them for your Extra Attack.
Okay, it's not a game changer, but it can't be that hard to implement to make this work properly and to leave regular bows as a viable alternative option.