2K19 was a great game.
Here's the thing, when most people hear game engine, they tend to think way to rigidly. Its not a simple factor of "game engine old therefore bad". It can be limiting if something in the engine wasn't built to handle an idea (for instance, the current WWE games engine is not built to handle submission holds from a turnbuckle that go into the submission mini-game, thus why the turnbuckle Bully Choke or whatever Brian kendrick changed it to is just a regular impact move). But the engine like anything else is still a bundle of code that can be edited and modified by talented coders.
The main problem, of course, is time. Working on an engine, whether modifying an existing one or creating a new one, is a lot more involved than just making a game using the engine. The issue is not that the engine is bad or anything of the like, the problem is A: They brought in a bunch of new coders who had absolutely no experience with the thing for 2K20, B: they used 2K18 as the base for some idiotic reason even though 2K19 had already fixed up a lot of stuff. C : (*Censored* off emojis) from what I can tell, Yukes coding is already rather messy and any programmer will tell you trying to read someone elses code if it isn't extremely well done is like pulling teeth. D : (seriously, *Censored* off emojis) 2K20s issues from what i've heard was not just code related.
Do I think a great game can be made on the current engine? Of course I do, Skyrim was made on the same engine, albeit modified, as Oblivion, Fallout 3, and Morrowind. WWE 2K19, while still rather buggy, was made on the same engine as 2K18 and 2K20. I also am aware that they would need a lot of time off (in-office as well, and likely 2 or 3 years just working on the engine without even using it to make a game) to make a new engine that wouldn't have enormous caveats, sloppy code, or severe oversights.
The goal here for 2K needs to not be "oh no engine bad we need new engine now plz yes", it needs to be sitting everyone down, getting familiar with the code and how it all works, dedicating some goddamn time to bug testing and fixing, management that doesn't sit around on their ass and leave everyone with no clue what they're doing, and a willingness to stand up to 2K and WWE and say "if we release this broken, its going to be another disaster. If we need extra time, give us the goddamn extra time".
2K20 was in my personal opinion the culmination of multiple issues with Yukes departure acting as the catalyst to trigger them. I am of the personal opinion Yukes leaving is not a bad thing, they are not blameless in the issues the games have had for years, and going across the pond on a constant basis to make a game every year was eventually going to blow up in their faces. The problem is the suddenness of it all, and no one thinking ahead. The engines age is actually something of a minor factor, I think, in it all. Whats needed is time, talent, and common sense.
The upcoming competition might also be a nice kick in the ass which the series has sorely needed.