Not my diagnosis. In 2016 those were hardly problems; fodder did not spawn infinitely, nor did your chainsaw fuel, so you had to ration them as you dealt with heavier units. As for health drops, they were generally proportional to the amount of health you had. On lower difficulties they were way too generous, but on UV and higher unless you were under half health enemies would not drop enough health for you to count on it keeping you alive on its own. It absolutely can work, but it takes some tweaking of the numbers. The resource return added an interesting element of risk versus reward that can work incredibly well when executed properly. Ultrakill is a great example of this principle in action. 2016's main problem is that the numbers were too lenient on the middle and mid-low difficulty levels.
You can trace the problems with Doom Eternal back to the addition of the Meathook and Dash. Both were cool features that made mobility a lot more fun. However, they also made Doomguy way too OP, so they had to start heaping on new mechanics and new enemies with much more specific strengths and weaknesses that started to pigeonhole the playstyle of the game and make the increased difficulty, while legitimate, much less satisfying and less fun to replay compared to its predecessor. 2016 to me was the sweet spot. If they had just made 2016 with better graphics, minor tweaks, and more maps, it would have been much better long term. They tried to fix a formula that was simply not broken and ended up over-engineering it. They made fights longer and more drawn out, so they had to make the chainsaw and glory kills a regular part of the loop rather than something you resorted to in a pinch. That was where that mechanic went wrong.
I think there's merit to the way Doom Eternal does things. It has its own combat loop, it does have its own legitimate form of difficulty, and the gameplay can be really damn fun at times. It would be even more so if they split up the missions to be less insanely long. Its main flaw is that it's busy and chaotic to a fault, and I certainly don't find it as fun as I did a year ago. But I do still think the foundation it was built on, the Doom 2016 mechanics, was rock-solid. I can understand disliking it from a basis of preference but I think overall the glory kill/chainsaw mechanic worked and worked well when better constrained by finite resources.
