multiplayer is not well implemented at all. there is no way to communicate with others not even emotes ( at least that i know). i played a level today with another person and we did root mother together. then i had to go and coouldnt even say goodbye. i disconnected after the checkpoint and i left the guy there. there is also the problem to join games : you are not sure if the person is gonna rest to a checkpoint soon and a lot of people leave before you reach one. i had several times this happen while running back to checkpoint to spawn prople, but without a way to communicate they coouldnt know
There's voice chat and emotes. You just can't text each other.
Multiplayer seems very well implemented to me. I get the impression that Remnant was designed for squad play (max 3 players though). I've watched some big Twitch streamers like Summit1g (FPS pro) playing multiplayer (full playthrough) and loving it.
Was ok in coop with my brother but i don't see it as a strong solo title. There are too few weapons and enemy types, it gets old fairly quickly shooting the same stuff with the same weapon the whole time. The upgrade system feels pointless, apparently due to the scaling as i take it from other posts. I always upgraded my stuff when i had the resources to do so and therefore always used my upgraded weapon and had no incentive to switch weapons. However the basic mechanics for shooting is solid. I only play coop games side-by-side with people that i know, i don't know how it works out with random people.
There's at least 15 big guns, 9 small guns, and 16 melee weapons. There's also 22 mods that can be applied. I've found the weapons to be very distinct from each other, suiting many different playstyles. But most of them need to be unlocked (through boss fights or special zones/encounters), so yeah the initial selection can be a bit limited.