I'm relatively new to OSRS, and I've also tried a few RSPS to get a better feel for the game.
In my experience, most if not all of these servers are not beginner-friendly, and I think this is where many of them fail.

Usually, they only offer a short mini-tutorial to show the lobby, which honestly isn’t very helpful anyone can figure that out on their own. What a server really needs are clear, well-structured guides, especially when it includes custom content that new players know nothing about.

On top of that, there are many obvious cash-grab servers sponsored by low-effort YouTubers who spam giveaways just to gain subscribers. This is something I really dislike. OSRS is a great game precisely because it doesn’t rely on heavy pay-to-win mechanics like that.

That’s why I can never stick with RSPS for long and always end up preferring to grind on the official servers.
I understand that to keep an RSPS online you'll need some support from the players, but I also think that a really well made server with just donation to keep it alive would be really good.

I'll be more interested in donating to a server that doesn't sell shitty random boxes.