"All the other systems in Retropie and not in Recalbox such as 3DO or Jaguar are unusable they are too slow (less then 10 FPS)"
That's just not true.
Retropie emulates the Atari 5200 console and the 8 bit Atari computers (eg the 800XL) perfectly, and picking another few examples at random, the Dragon 32, Oric, and TRS computer emulators also run perfectly on Retropie.
Admittedly, the only systems I think the majority of users would like to see on Recalbox would be the Atari stuff that is missing.