It was marketed as a Turn Based Close to Tabletop D&D Experience. We are not getting that. End of story.
Is there a source that says Larian wanted to create an authentic TT RPG? [...] I don't remember Larian guaranteeing or even promising such a thing.
I tried to answer that question in that post, a little while ago (motivated by a similar question from someone else). My understanding of Larian's vision has probably improved since then, but the core of my post was looking at 4 interviews Larian gave, where they talked about the rules and the DnD/tabletop feel, and what they said won't change.
I wasn't able to provide a definite, clear-cut, yes/no answer to the question. But I found their communication to send mixed signals, saying both "it will be quite close/just some tweaks" and "oh we only focus on a game we'll enjoy playing, not so much on the RAW". And I think that it is very understandable that, as a result from Larian's communications, some players were expecting more faithfulness to the rules.
Right. Again, my expectations were the same as both of you. I'm just saying Larian had very slick attorneys that made sure whatever they said or promised never mentions an authentic 5e experience. And probably will never say one way or another. And why would they? They would end up alienating a whole portion of their audience or worse, promise something that may not or cannot happen.