>when you need to write a functionality that is specific to your game, and it becomes too dependent on a certain engine or library, so you can't switch to anoth

>when you need to write a functionality that is specific to your game, and it becomes too dependent on a certain engine or library, so you can't switch to another library or engine. Games are not a thing you just change engines on. You don't paint with oil on a canvas then halfway through it go "you know what, I think aquarelle would be better" and swap out the canvas for aquarelle paper. The engine is a detail of your game and should never be core to it. >but then it doesn't leave enough room to add new cool things, like cool gameplay, a good multiplayer system, etc, when you want to ship on console who have limited memory. You've not given a single look at Unreal, have you ? You have complete access to the entire source, it is modifiable and extendable to do absolutely anything you want, whether through blueprints or directly in C++. No cool multiplayer ? UE's default network replication is good enough to run on pretty much anything today. No cool gameplay ? ABZU (adventure puzzle exploring game), Assetto Corsa Competizione (highly accurate sim racing), Borderlands 3 (FPS Loot shooter), Dragon Ball FighterZ (fighting) as well as many experiments by users, including complex uses of portals and non euclidean geometry, etc. It's not that the engine doesn't let you do cool things, it's that you're a software developer at heart that wants to find reasons to add new features to your engine, instead of making a game. >PUBG is a similar game, but its performances are quite bad PUBG was made by a brand new developer who slapped together assets from the store and hacked away until it barely worked. The whole core of PUBG is rotten and terrible code. So, sure, with home made engine, you don't have this problem because someone like Playerunknown would literally not have had the skills to write the engine and the game would have never existed. It's not an engine problem, it's a developer problem. Think about things for a minute when you do then and you'll have no troubles. It provides you with so many accurate and useful debugging tools that your home made engine will never have if you want to do a performance pass.