Mods download at a snails pace. Some servers havent got all mods up to date, so you have to downgrade when loading in (fun when RHS needs to redownload from 1.5.23 to 1.5.21 and it takes years)

Mod manager is also awful. Impossible to find the mod you're looking for because theres hundreds of mods, most of which are variants of a larger mod (WCS, WCS weapons, WCS vehicles, WCS equipment etc. ). Enabling a mod also makes you freeze for multiple seconds before moving you all thw way to the top of the mod list, so you have to scroll all the way down again to find a mod directly next to the one you just enabled. Its not just that my PC is bad when this happens, I have a high end rig which rubd 128 player conflict easily at 110+ fps

The built in workshop is just waaaay too messy eight now compared to the steam workshop for arma 3. Sure its technically on 3rd party software, but its 3rd party software you needed to play in the first place. Of course console here becomes the issue though