@Geen I hear ya loud and clear. This actually happened before in Manthano 1 as well.
I just rolled out a new feature to help us better manage this. You can read the details here but the gist is that instead of having to boot people, impose time limits, or mess with the galaxy size, we can force random secession on players who go over the intended planet limit.
Better yet, we can adjust the limit on the fly too. We just freed up 278 planets (about 18% of the galaxy) to be re-explorable, but if that’s still not enough we can lower the limit even more.
Planets secede at random, so this should include planets close to home systems.