Is it still worth to create a GmodRp Server ?

Yes it's worth it, at least for me. You need to set up a goal and vision on your server like where it will go? how it will go? You'll need preparations and resources for running a server. Good planning can lead to a successful server.

Once successful, you can start creating or commissioning custom contents. Spending money is always a risk, but it's a risk you'll have to take when making a server. Maybe you can start free, then once you get donations, start using it on custom contents. People will love and donate more for custom contents whether it's models, maps, weapons. So yeah.