As someone who’s played a lot of games… I disagree. These days I specifically avoid Unity games because they always feel janky, and yes it absolutely is the engine.
As someone who has used Unity a lot, it really isn't the engine. You're only noticing this is the whole "no good toupees" thing. The thing is, the Unity Assetstore makes it very easy to hack together something that kind of works, but because nothing will quite fit together it'll be a janky mess.
I don’t take it to that extreme, there’s great Unity content (walkabout VR mini golf comes to mind), but recently when I really played an Unreal Engine game again for hours (Satisfactory), I was floored by just how much better optimized it was. A similar, arguably simpler, game in the genre (Oxygen Not Included) is Unity and famously terrible on performance. I had just sort of accepted that was how it had to be. It’s not.
Oxygen Not Included is a _significantly_ more complex simulation than Satisfactory is as ONI is doing gas movement & thermal transfer mechanics across a large 2D grid.
Now compare Satisfactory to its actual genre-appropriate competitor, Factorio, and suddenly Unreal looks like a pathic joke. Factorio scales _so_ much better it's absurd, but that's really down to the quality & focus of the simulations being added by the game developer. None of it has anything to do with the engine itself (well, except that Satisfactory is limited by the number of game objects it can place as a result of an Unreal Engine limitation...)
I'd expect it to be equivalent since the task the engines are doing is well within both of their respective capabilities.
The engine is not simulating any of the factory logistics, that's all going to be bespoke code by the game dev and so there's no major reason to expect unity or unreal to behave meaningfully different here.
Tarkov is a bad example. The devs are absolutely FLOGGING the entity count and their maps are huge with lots of little details. People give them crap for doing a bad job but the vision they have for the game would be difficult to pull off no matter the engine. They have been on an old version of Unity for a while and are currently moving to a newer version.
One big argument people have is whether the lighting in game is good or not. They do dynamic lighting, which can definitely cause some voidlike shadows, but people were arguing over whether Unity had tools to help with that or not.
Also, multiplayer is hard, but they have made some (very questionable) decisions like sending all clients the entire map entity list. Hackers abuse this to know where rare items are located and even the stuff other players have found or brought into raid. If I find a GPU or LEDX and put it in my bag, they instantly know and can come kill you to take it. This combined with issues with desync, audio not working correctly, invisible players...I don't think this is a Unity problem as much as it's just a complex game, a pretty small dev team, and they don't want to hire outside of Russia.
Tarkov, while a great game, is very janky, and has a cheater problem. I have heard these things attributed to Unity, though I am not familiar enough with the details to say that's absolutely true.
Rust is fine though, in my experience. (and yes I do mean the video game in this context, hahaha)
For comparison, Unreal games that don't get extra optimization and love during development have engine-standard issues. Star Wars Jedi: Fallen Order is notoriously affected by Unreal load/unload lag spikes, even on console. Every Unreal game will do this to some extent unless that behavior is dealt with since it's just how Unreal handles large texture swaps.
So yes, an engine can have known issues, but isn't it up to the devs to make a product that runs well? Unfortunately for Jedi: Fallen Order they just weren't given time to make it work well, just "good enough" for console, and it's even worse on PC. The sequel has the same issues.
Haven't experienced a single issue playing BattleTech, which is Unity. Based on the sheer number of games built on Unity I'm sure you'll find plenty of games that are janky because they weren't made well. That's not the engine.
Having played a lot of games isn't really much of a qualification, is it? I'm curious about your claim that Unity games "always feel janky". Which games gave you this impression?
Basically every famous unity game? Like Cities Skyline has always been a complete disaster. So is Kerbal Space Program and in Dyson Sphere Program there are all kind of issues where once your map reaches a certain complexity the game just falls over, and save files bloat to hundreds of megabytes.
What are you referring to with Cities: Skylines? I've never had any issues with it, it's a pretty polished game. The real issues only start cropping up after installing tons of mods on top of it.
And yeah, I feel like you're choosing some specific games while ignoring all the others. Tons of famous Unity games are great. Is Subnautica janky? What about Hollow Knight? Rimworld, Beat Saber, Outer Wilds, Cuphead, both Ori games - the list of major Unity projects can go on for a while, and I wouldn't call any of the above examples janky.
The Ori games have terrible performance for pre-rendered 2d graphics. That's the exact kind of jank I'm talking about. Tons of microstutters. It's like using a '90s Java GUI app.
Really? I can't say my experience matches that at all. Hell, the developers got both games running on outdated Switch hardware at 60fps, even in handheld mode.
And even then, as far as I know, they're not really simple 2D games, but more of 2.5D. There are 3D background layers and 3D-like lighting and effect calculations, in addition to overall being very visually dense and complex. I certainly can't compare it to fully flat games, like the aforementioned Hollow Knight or Cuphead, etc.
Yes: I could make the crashed burning spaceship pop into and out of existence by walking a couple of metres back and forth across the floating platform I was standing on.
As someone who has used Unity a lot, it really isn't the engine. You're only noticing this is the whole "no good toupees" thing. The thing is, the Unity Assetstore makes it very easy to hack together something that kind of works, but because nothing will quite fit together it'll be a janky mess.