His point is wrong then.
If you create a simplified version of something, and something that stays pretty true to the PnP system, the hardcore crowd's gonna gravitate towards the hardcore thing.
PoE and Deadfire to a larger extent was trying to bridge the gap between the mouthbreathers who like D:OS and 3.5 D&D Chads, such as myself.
Hardcore crowd buys and plays all these games even when they pretend they don't. Josh repeatedly has said the hardcore Kingmaker type crowd bought the game, and that they were not the problem. I know you want to feel like your divine hardcore judgment doomed the game to failure, but the small niche of Kingmakersexuals aren't that important. PoE2 failed because it didn't get the Divinity OS crowd back for the second go, as he has repeatedly said. The postmortem question is "why did they lose that crowd?" It's literally the opposite of your assertion that the game wasn't pleasing the hardcore enough.
As others have suggested, I think the main problem was probably that PoE1's story and game world were kinda boring.