I completely agree with your points. My relationship started out as polyamorous - I was joining a poly relationship that my partner had. And while he loved me very very much (we see each other as soulmates) that nonetheless didn't always translate to "having enough time for me".

I also experimented with having a girlfriend during COVID - this emotional energy took away from my ability to focus on my primary partner.

For now, we are monogamous. It may not always be that way. But we're more aware now that just because theoretically "love is infinite" does not mean time and energy is.

And my time and energy is also split between my romantic partner and all my platonic friends, let alone work and alone time. So I don't really have any bandwidth for another partner.