The reason Pokemon was more successful than Digimon is because Pokemon only has the fun parts of raising a monster pet but Digimon forces players to spend an extremely large amount of time on the lame and annoying parts of raising a pet.
>cleaning up your pets crap mechanics
>your pet fucking dies of old age mechanics
>training your pet is tedious and time consuming
>your pet might unexpectedly turn into a turd if your stats don't match some invisible spreadsheet requirements

thank god Digimon has been moving more and more away from these bullshit mechanics and removing them in more modern games.