A few points:
1) It's just the first part of the game. I did the EA for Divinity 2, loved it, and loved playing through it "for real" when the full game came out. There was SO much more to the full game that re-playing just the first part with a different party was still plenty of fun. BG3 is *much* larger than Divinity 2, so the EA is an even smaller chunk of the final game.
2) Regardless of positive/negative commentary, the advantage of this kind of EA is that the developers have thousands and thousands of play-testers instead of just a small group. They collect data on how the game is being played, where people are dying "too much", which encounters are too easy, and perhaps most importantly, bugs that might not show up with just a small group of testers. This improves quality of the final product and does it faster than with a wide release that has tons of bugs.
3) If you don't like Divinity 1/2 and you want a game like the old BG1/2 (both of which I loved), you're out of luck. I loved all four of those games, so I'm more than happy to buy it now and play *now* rather than wait even longer than I've already waited.