EA forgot to implement non active family be able to register for resort or something because they basically just visisting and standing around, doing nothing but chatting for every object is for registered sims only.
Whats the point of having resort if thats so anyway? Is there away to make resorts free for all or paying is optional? Its the only lot type able to function hotel-like,

As buggy as some EA gameplay can be, the resorts are very much capable of functioning as intended. It sounds a little counterintuitive to try and find a workaround for something that sounds like a glitch or a mod issue. Maybe even an oversight in the build itself?
There should both be sims who check in and sims who use the general facilities that aren't behind locked doors. The amount of real sims actively there doing things will also vary based on your game performance.

Overwatch has some resort related fixes, so does Register for resort workers.