While I regularly play with the Izayo Weapons Pack, I'd have to agree. The base game does not need more guns. The problem with adding more, as was mentioned, is that the game already covers the general categories. And because this isn't a pure realistic shooter, they are not going to pay licenses for adding real-life weapons.
Now I would fully support them making the gun play better, though. While I understand and have argued in the past that this game leans into more arcade-style when it comes to gun play, after having played with the Izzy's guns, it is SO much more satisfying when the guns animate, behave, and sound more realistic. It's the little details. Plus using the actual iron sights for aiming is oddly better (weird idea, I know).
But I'd be fine if they left it as is because, again, mods. Erm, sorry console players?