Servers only have a limit as much as they can handle, depending on your time zone some are more populated than others.
https://starmade-servers.com/ Have a look and pick a server you like. Just a warning that on the extremes of player activity servers can get laggy.
Anyway you can use the demo version if you want to try starmade out, if you are using steam the option is on the right side. Right now the demo is the same version as release with no restrictions but that is very very likely to change in the future.
Right now I see one server with nearly 70 people and a couple in the high 30-40s. So is that plenty for you?
(remember to check past the first page, since many servers use bots to spam votes and increase their position or other means)