Hi!
Objectively, from the game mechanics perspective, Deadfire is the superior system.
One can still dislike the changes from PoE to Deadfire of course - but often that seems to stem from the fact that people don't welcome any changes to something the liked in general, even if the changes are for the better.
I felt the same way initially when Deadfire's beta came out (there is still a ranting post from me to be found here in the forums somewhere). I was just disappointed that they didn't keep the rules as they were instead of re-inventing the wheel - but I came around eventually once I got used to the changes and once I got an overall better grasp of the game and its new systems.
I would suggest you give it a bit more time. I think it's totally worth it.
Here are some changes to game systems which are improvements:
power level scaling makes sure that low level abilities and spells scale/progress and stay impactful. For example: unlike PoE's Magic Missiles which are basically useless in the later game, Deadfire's Power Level scaling adds more and more missiles to that spell so that it's still worth casting even in the game
the (multi)class system works very well and allows for a lot of interesting and fun to play combos. In PoE we only got some cross-class talents.
the affliction/inspirations system is more intuitive and practical than PoE's affliction system which had no solid structure. It's also more tactical because you can counter afflictions with the fitting inspirations (and not only Priests' prayer spells) - and you get resistances and immunities on top
While I miss the 6th party member, the endurance/health system and per-rest spells, the new approach (party of 5, only health, per-encounter spells) have their advantages, too. Mainly it made it easier to design and balance encounters - and imo one can feel and see that: a lot less meaningless filler fights for example.
the PEN/AR scales much better with your progression than PoE's DR did (even though it's a bit too punishing on PotD imo)
stealth in combination with sneaking and pickpocketing is just no comparison to PoE (pickpocket wasn't even possible)
the interrupt/concentration system is a lot more tactical and not just an uncontrollable side effect it was in PoE - instead the interrupt is a powerful tool and having concentration is a meaningful protection against it
unique item enchantments in PoE were not that diversified, the enchantment system is pretty generic: you put the same enchantments on every weapon/armor. In Deadfire every unique item has a unique enchtantment and weapons and armor have unique upgrade "trees" with interesting effects - many of them lead to cool combinations with certain (multi)class abilities which are fun to explore
Deadfire has a nice UI-based AI-"if this than that"-scripting tool which is leages better than anything you can do with PoE's party AI settings
pets (not the Ranger's Animal Companion) which were only cosmetic in PoE have useful individual and party-wide effects now in Deadfire
the new weapon proficiencies grant you a weapon modal but the system doesn't give non-proficient weapons disadvantages - PoE's weapon focus soft-locked you out of certain weapon choices
you can export party members as hireligs for other playthroughs
the stacking rules are much less obscure and less "all over the place" in Deadfire
the combat log is a lot more detailed and helpful
the character info (currect stats, effects etc.) is more detailed
And so on and so forth...
I personally liked the tone and "vibes" of PoE better than Deadfire, I also liked the main story of PoE more - but the systems design of Deadfire is way, way better than PoE's.
While it's absolutely valid to dislike the changes made (initially of forever) - a game has to meet your taste after all for you to be happy with it after all - it's not right to call Deadfire's game system inferior.
Mechanically Avowed is nothing like PoE... or Deadfire either (unfortunately). Besides it being a first person, real time action RPG (like Skyrim etc.), it also has more streamlined character creation and progression systems, UI etc. due ot it being developed for gaming consoles (and therefore gamepads) as well. PoE and Deadfire were originally designed for PC only and their mechanics and the UI options are a lot more intricate. Outer Worlds stuff is the same as Avowed in that regard basically.
There are lots of mods for Deadfire and they are easy to install and manage (Deadfire has a build-in mod manager - another plus). I took a quick look but cannot find any mod which would introduce a whole bunch of PoE rules into Deadfire - besides some minor things like putting PoE's Riposte chances into Deadfire - or some unique items. Here's an overview:
https://www.nexusmods.com/games/pillarsofeternity2/mods?sort=createdAt
Cheers!