NexoCraft is a Java server for players on versions 1.16 through 1.20. Joining is simple: open Multiplayer, add the server, enter nexocraft.org, hit Done, and jump in.
The server is built around Survival, PvP, PvE, KitPvP, and Parkour, so there is a mix of fighting, challenge runs, and more relaxed gameplay depending on what you feel like doing. It also looks like a good fit for players who want a straightforward public server without a bunch of extra setup.
If you just want something easy to join and play on with a bigger player cap, NexoCraft keeps it pretty simple and open.