yeah thats our biggest cause of lag, we used the timings report from paper to find regions that were really bad. One player had about 200 villagers each in their own boat so that was a big cause whenever they would log on.
I just followed the optimization guide https://www.spigotmc.org/threads/guide-server-optimization⚡.283181/
and especially the pillager limiter plugin helped a lot. Everyone had an army of pillagers outside their base which was annoying and laggy