Wow.
We are still debating if PoE was unsuccessful for the mechanics.
We're not, obvious facts don't need to be debated.
What makes people think that the mechanics were the cause is something I do not understand. I gladly acknowledge that I *speculate* that it was the setting and the storytelling. But the mechanics side seems to have "facts" in their hand. I would be interested in knowing what they are.
The kind of changes Obsidian have done to mechanics clearly indicate there was some massive problem they were trying to mitigate. First game on launch was so easy, it could be effortlessly beaten on PoTD just by selecting entire party and left clicking on target after target. And yet they decided to spend considerable resources onto making additional difficulty mode that makes everything drastically easier.
I'm not sure if I ever actually heard about any game other than Pillars having to be patched with Extremely Easy difficulty mode after launch. You don't do that unless significant portion of your playerbase is doing something you didn't predict.
Then you have mechanical changes in Deadfire which are drastic and focus on decluttering and simplifying the combat, which is an incredibly strange thing to do in a sequel to something as unexpectedly successful as PoE1. If your indie game becomes a smashing hit, you stick to the winning formula, not rework everything from the ground up. And the only explanation that makes sense is that all that telemetry shows people only liked the game despite the mechanics, not because of them.
It's also a fact that the one of most common complaints you'll see on mainstream forums and social media is that combat is an incomprehensible clusterfuck.
So yes, mechanics are the problem. They are not they only problem, main quest in both games sucks and that doesn't help, making a direct sequel to the game that a lot of people bought, but few people finished, was a dumb idea, and we could go on and on. But the fact that IE-style party based RtWP is costing them sales is not up to debate.