The Witness was a slog, maybe he's learnt how to make puzzles which are actually fun this time.
There's a pivotal moment where (assuming you find it at all, which isn't a given) your entire perception of the game world flips around, and walking back through environments you've already explored you're now perceiving them in a completely new way. The closest thing from fiction I can think of is the big reveal in Fight Club, in that it puts the entire plot in new light, except in The Witness the flip is basically unrelated to any of the "content" of the game. Very very impressively done.
It's weird that people seem to really have latched on to some off-the-cuff remarks Blow made on stream about not being an atheist (even though he also called out the false dichotomy between naive atheism and literal interpretation of Christianity). Blow has been open about his experiences with meditation practice and its influence on his game design, and I think it shows. I'm not personally a huge fan of the type of games he makes, but the thing he seems to be aiming for in his use of the medium are interesting enough that I'm definitely going to pay attention.
However, I do understand why some consider it a slog. There are many puzzles in the game that people will dislike, indeed many puzzles that I disliked. It seems Jon prioritized finding all of the interesting things that they could say about the puzzles in the game over making sure that all of the puzzles were actually enjoyable to a majority of people. My advice is if you don't like an area, just go somewhere else. You don't need to complete every area to roll credits.
It also may be a matter of expectations. Puzzle games tend to be on the shorter side, but The Witness is lengthy. So jumping in expecting to finish in an afternoon is a way to set yourself up for frustration.
I think Blow achieved what he wanted, which I guess makes it a good game in a sense but also it wasn't an experience I enjoyed or can easily recommend to others.