You can make good games without new ideas. Johto is just a refinement, after all. They just had to lean harder into being a real JRPG, by designing memorable combat encounters, having a quickly paced story, real level design/dungeons, etc. SMT is a franchise that continues to advance despite not really overhauling the ruleset since adding demon negotiations and fusion.
They just stopped trying to compete even with a lack of ideas. Gen 5 was a real RPG and after that they've just been coasting in a very transparent fashion.
