Anything that loads a map into the world, causes major server-side lag

This has been reported, and the bug says it's fixed in MC-126244 as well as MC-236740 - but this is still an issue in current versions.

This mainly appears to be an issue if the structure being looked for is far away.
The best way I was able to replicate this for this issue was by using the /place feature to place a shipwreck on land.
This is also an issue if you're leveling up cartographers in an area that is nowhere near the ocean or a mansion.

I've attached 2 videos and JFR reports for both of those, as well as the server log