I'm sorry you had a bad experience with Unity.
However : don't worry, ianov, I'll help you with that when I come back home tonight or tomorrow :)
You'll be able to use RPG Maker with it !
Oki, just send me a mail at xxxxx with your unity store receipt ☺️.
For the record : lecagy tilepalette was the only palette in the v1 of the unity asset pack.
The current tilepalette came around the v2 and is, in my opinion, better organized (as you said), but some assets didn't make there (obscolete tiles).
You can use both, it's why the legacy is still available 😊👍