Them being overshadowed by bows is most likely intentional - crossbows' main advantage is that any random peasant can use it to lethal effect without much training, but as evidenced in the Crusades, a skilled troop of bowmen win - with lots of firepower on its own, if perhaps a bit inferior, but disproportionately larger rate of fire.
The main drawback of a bow is that it's a pain to create an army of bowmen, because it requires years and years of training.
Crossbows seem to get a bad rep these days, I blame British historical bias (Agincourt) and god damn Tolkien elves. I used to also think they were peasant weapons but after some reading it seems like I was completely wrong and it's better to look at the crossbow as having a completely different skillset and use then bows.
While it's true that a lot of crossbow use was by peasants that was also true for hunting bows. Every man in the country would know how to use either a hunting bow or crossbow and most urban men would have some knowledge of either. The advantage of course was that crossbows could have a much higher poundage than hunting bows and warbows (like longbows) needed extensive training (sometimes even before manhood).
Crusaders' crossbows were also devastating against the muslims especially during the first crusade. "Frankish Bows" as they were called were notorious and hated by the defenders, often outright killing or torturing captured crossbowmen.
Bows are basically artillery, you lob as many projectiles at a group as you can and you get the hell out of Dodge if they start making ground. While you can have great accuracy with a bow you have to reload the weapon, draw to full power and then take aim making it rather dubious at close range or when there's plenty of cover for the target to scamper behind.
A crossbow however can be fully reloaded, cocked and ready to be fired all before an engagement. All you have to do is aim and pull the lever. This makes it far more effective in a battlefield where enemies are drawing closer or even more suited to sieges. A crossbow is also much more suited to fighting from cover (like a pavise shield) where you could reload in safety and emerge only to take aim and shoot.
Since a draw can only be held for so long with bows they're not very effective at "sniping" or "tracking" enemies that are moving from cover to cover. A crossbow can be held at full effectiveness for until that short period where a mark withdraws from cover. Although pre-modern crossbows all lacked "sights" soldiers became pretty adept at aiming down a crossbow excelling them in long drawn out sieges where they could pick off patrolling guards and slowly draining manpower.
Crossbow skill mostly take the form of tracking, aiming and reloading. All of which could easily be rolled into a single perk that could rival power draw. Decreasing mouse acceleration (while in "ironsight mode"), weapon sway and finally reloading speed.
tl;dr: bows are artillery, lob as many projectiles as possible at the enemy clumps. Crossbows are the close range defensive tool that is also effective at picking off targets moving throughout cover.