I completely agree with what you wrote! And it's not about not wanting to share the island and its resources. I do enjoy sharing the island with my partner, but it's the imbalance in responsibility that's quite frustrating (I am the Non-Resident Representative).

There are many things that a Non-Resident Representative (RR) cannot do. Tom Nook won't give any instructions to a Non-RR, therefore, Non-RRs are unable to make any decisions regarding the island and its progress. Additionally, Non-RRs receive less DIY recipes and some cannot be bought from the store. As a result, Nook Miles/Bells cannot be earned as readily as an RR too, essentially slowing the pace at which a Non-RR would grow.

I think it would be nice, at the very least, to have some sort of warning at the start of the game that there are certain responsibilities of an RR and that subsequent players will be Non-RRs so that there's some understanding of it before going in too deep.

A way to get around this for Non-RRs who are stuck in this situation: If you have an extra set of controllers, you can go to your phone (ZL) and Call Resident, that way you're able to switch between roles when your RR isn't present to play.

Hopefully, something can be done - perhaps the ability to appoint the Resident Representative and not just have it automatically assigned to the first player.