So you don't like playing on big servers? That's ok. Actually there are more and more players nowadays whole prefer smaller servers will friendly communities be most of big servers are just too toxic or aggressive, while on smaller servers you can still have fun and just build. It's kinda like something for everyone…
The question is tho how can you find small Minecraft servers? Of course not only small Minecraft servers but also servers that have good uptime and will stay around. There are tons of small Minecraft servers that won't last simply because server owner doesn't have time or will to deal with it and once the server would shut down Minecraft players would lose all their builds and items.
It's generally best too look for servers that are not to competitive and were around for awhile now, it's unlikely that Minecraft server that was around for 1, 2 or even 3 years would just shut down tomorrow, but the same can not be said for server that was created yesterday and has no players at all.
That's where Minecraft server lists come into play, most of them would list Minecraft servers, their stats and age.
It's still good idea to check Minecraft server out, see if plugins are updated or broken and if server is properly maintained. You would also want to check out their staff team, as they're the one who will be helping you if something goes wrong, which is not that uncommon in Minecraft. If you can't find or reach any staff members or even see them listed on website, then that's probably a bad sign.