1. Engine choice is only a factor in performance. If you build an unoptimised game it will run poorly. Doesn't matter if you do it in Unity or your own engine.
2. Terraria, etc did not succeed because they use their own engines.
3. Those bad performance games have bad performance and happen to use an engine, not the other way round.
4. The quality of your game has a lot more to do with effort, care, etc than the engine you choose to use. You can create a buggy piece of crap no matter how you make it
5. Performance alone is a bad reason to roll your own engine. "Existing engines are not performant so you should roll your own" is a very bad piece of advice.
6. Making a good engine is HARD and a lot of effort. There is no guarantee that you produce anything better because you chose that path.
1. Engine choice is only a factor in performance. If you build an unoptimised game it will run poorly. Doesn't matter if you do it in Unity or your own engine. 2. Terraria, etc did not succeed because they use their own engines. 3. Those bad performance games have bad performance and happen to use an engine, not the other way round. 4. The quality of your game has a lot more to do with effort, care, etc than the engine you choose to use. You can create a buggy piece of crap no matter how you make it 5. Performance alone is a bad reason to roll your own engine. "Existing engines are not performant so you should roll your own" is a very bad piece of advice. 6. Making a good engine is HARD and a lot of effort. There is no guarantee that you produce anything better because you chose that path.