It's a cool fighting style absolutely. Buuuut it's very unrealistic that the handcrossbow has been essentiall turned into a glock.
Oh, I agree it's terribly unrealistic. I also don't care.
And that's a fundamental tension in D&D - plausibility vs "rule of cool". With all the movies, comic books etc etc, it almost is guaranteed that out there somewhere there is a cool protagonist being supercool with a ridiculous weapons. For example, I recall a certain film where the "Blue Rajah" threw forks and one of his allies threw a haunted bowling ball. Does that mean that forks should be a viable weapon in D&D? NO! But hand crossbows were turned into a superweapon, and calls for WotC to "make whips viable" are not rare.
I'd have no objection to hand crossbows doing d3 or d4 damage. Although, it looks like One D&D is going to include pistols. I guess I can just take 2 levels of Artificer and be the Gnome with Gno Gname.
Where do you draw the line?
I think I'm at a point where if we have wizards hurling firebolts all day and fireballs a handful of times without sweating (quite a feat to beat the heat!) and then for the finale creating a pocket dimension for a meal or to store untold loot, that I think I'd like the option to include some minimal magical tricks for everyone else. Especially when darkvision is just a thing. Nobody's biological eyes work like that without magic, but the game seems afraid to say, "Oh, yeah, that's actually just magic."
I mean, Crossbow Expert allows a high-level Fighter, with a surge of adrenaline, to fire a heavy crossbow 8 times in 6 seconds, and we're to believe that's
not magic? A heavy crossbow that requires a windlass or crow's foot to span it? When light crossbows historically had a battlefield rate of fire around 2 to 4 per
minute? That's at least a 20-fold increase in firepower. It's
double the specified rate of fire of the M1 Garand (40-50 shots/minute), meaning it's got a higher aimed rate of fire than the semi-automatic rifle credited as "the greatest battle implement ever devised" precisely because of how it enhanced the firepower of infantry. Nobody is that much of an expert! Like the magic is already there. We're just in denial about it.
This is the thing with D&D. We've got this heavy bold culture of "no magic unless caster! NO MAGIC UNLESS MAGICIAN! ONLY SPELLS IF MAGICIAN!" But we've also got a game with this pervasive problem that casters are a lot of fun and get really powerful and have a lot of dynamic choices, while martials... mostly decide whom to attack just like they did at level 1. And one of them scales really well, while the other struggles to stay relevant.
So we have this situation where martials have to stick to reality because they're "not magic," so when we improve them we're obliged to only let them do things you arbitrarily accomplish in 15th century Europe. Meanwhile, casters can do whatever you can imagine from fiction? Well no wonder it's broke! There's your problem.
I just... I don't find "that's not realistic" to be not only a credible defense anymore, I don't think it's a
desirable defense anymore.