Thank you all for your answers :)

Cerbion. Yes I really want to make a Diablo-like game and I dislike rpg-make movement and combat in the scope of this project. I know a tiny bit of Java script from scripting entities on minecraft mods, thank you for your advice ! I'm going to try to make a tiny game with few mecanics that I plan to involve in the greater project I have.

I think I'm going to stick to flare engine for the moment since it really looks like it's the best engine to make the game I want to create. Yet it's missing a LOT of informations on how to actually do stuff compared to more popular engines so I'm making baby steps.

Thank you for your encouragments ! :)

MedicineStorm Ok perfect ! Yes I do not feel lost towards how stuff works, the only issues I'm having is with a lot of problems (crashes...) That I really struggle to fix since there lacks a lot of informations on the engine.  But yes actually my will to create a game based of flare engine comes from me enjoying the game (reminds me of dungeon siege) and I felt like this engine could be a nice way to create an old school game quite easily, without having to deal with all the learning curve to be able to create this type of game in an engine like unity or unreal engine (wich would really feel like using a bazooka to kill a fly)

SuperGamersGames Thank you for your advice, I might be wrong, but I think I saw somewhere that GameMaker Studio 2 was really not the best to make an isometric tile-based game... I will check it out anyway but the thing is that Flare is made to handle such games as the one I want to create (isometric hacknslash rpg) therefore I feel like it's the best option...