Ya, even I prefer DOOM 2016 over Eternal. In Eternal, they introduced more parkour mechanics for the player, and we have to constantly jump, dash to reach high places. It was in excess. The game was also a bit more fast-paced. Doom 2016 was a much better title.
Honestly speaking, I got a bit frustrated by these mechanics on Eternal, but overall the good was pretty good. But AMMO is also scare in Eternal compared to 2016. I have not played the Ancient Gods DLC though. I don't feel like buying them. Are they worth the purchase ?
It's not that I prefer Doom 2016 over Eternal, it's just that when I'm tired, like I have been lately due to a lot of nights with 6 hours or less sleep, it's more comfortable to pick up and play, as it's not as frenetic a pace as Eternal. In fact I had quite the opposite feeling about the platforming in Eternal as you do. At first there were sections I had to take numerous tries at just to get through. However once I got to know the game better and improved my jump, dash, and lache techniques, most of which come down to getting in a rhythm with the timing of them, I got to where I could not only ace them, but shortcut a lot of them.
As far as aerial combat and super fast switching of multiple weapons goes, that can be very difficult too, but I found it isn't really as necessary as some would lead you to believe. This is the single biggest thing, other than demonstrating proper platforming techniques, that motivated me to do a complete walkthrough of the game on Nightmare. It was aimed specifically at showing how you can beat the game without a lot of fancy aerial combat and super fast switching of multiple weapons. As far as platforming goes, besides properly timing jumps and dashes, sometimes all it takes is mouse looking the right direction to accomplish what you want to do. like looking straight up to mantle a ledge you're hanging from.
And ammo is only scarce in Eternal if the player forgets to chainsaw now and then, which provides ammo and a bit of health too if I recall. In fact regularly using flame belch, both grenade types, glory kills, and chain sawing, are all essential parts of the combat loop. Most that claim the game is too hard don't use these tactics often enough, and I didn't myself the first play through or two. Eternal is a game that can take a few play throughs to master, and that is a big part of why I liked it so much. Being 64 though, I can't recover from nights with little sleep as well as I used to, so I like to have games like 2016 for those times.
I don't think The Ancient Gods DLCs would be to your liking. If you didn't like Eternal, you will dislike The Ancient Gods even more, for the same reasons. It throws a TON of tough enemies at you, with Imps running around tossing fire balls at you at the same time. I'll put it this way, in Eternal, even in the toughest battles, I could usually clear a small area at a time, then move to other areas, even on Nightmare. In The Ancient Gods, you pretty much have to keep moving constantly just to survive on Hurt Me Plenty, which is Normal or Medium difficulty.
Now granted, like I said, you start The Ancient Gods with all weapons and skills unlocked, but you soon see why when you start playing it. I only played most of the way through the first mission, and just once, so of course I could improve with more play throughs as I did with the base game. I may even wait until I build a new PC before I play it again.