Too many mobs!

In my public Minecraft server running on Spigot 1.16.4, we are experiencing an insane amount of mobs spawning in the game, almost to the point that it's unplayable.

All config regarding mob spawns are set to default, and I'm not sure where to change it. Alongside this issue, it seems like night-time lasts much longer than daytime, though I haven't actually measured this myself. That is just how it feels at the moment.



Can I get some help with this?