Well, after having a chat with COO of Horus (game studio), now I know that there are Vietnamese teams also made their own game engine, including big teams, but they ended up throwing their engines away for many reasons.
Horus and JOY Entertainment spent 2 years on the engine and 1 year for the game but now they're using another engine (maybe Unity or Unreal). He also advised me to give up my engine development because that would be a huge mistake like his team had made.
I told him that we were on different paths right from the start, he (and most of companies) wanted games but I aimed for technology and that's why I make an engine and use it to make my own games.
I myself has been learning about game engine for years, that's different from a bunch of people who only learn programming and software development jumping into game industry and try to make an engine like any foreign game company could (other countries have good base of game development to support that). So I keep believing the path that I've chosen.
My own advices for young game developers: If you want to make games, use anything to make good games, game engine is another story, don't spend time to seriously make one until you're sure that's what you need and prepare a good development plan for it.