Good post. On one hand, I agree. They had the opportunity to make some really crazy stuff with their own IP, and they didn't do that at all. My assumption is that they spent too much time on creating all those classes and making them all work, so a lot of their good ideas were distributed across different classes. (Of course, they should still have made, say, Cipher spells more distinctly different from mage spells.)
On the other hand, nearly every single example you cite from IE games are 6th or higher level spells. That is, the original Baldur's Gate didn't have Spell Trap, Wish, FoD... I don't think it had any sequencers, either. POE spellbooks sseem to have slots up to Level 10, and we only get to 6. Given 'm pretty willing to cut them a break as long as they continue to improve; if they don't, then they'll never have anything close to matching BG2.
I don't expect to see a lot of systemic improvements in the White March, especially because they cut the expansion into two (a horrible idea). But I do expect to see a bit more thought gone into encounter setup; a bit more out-of-the-way quest design now that they're using existing assets; and a bit less uneven writing quality that gets back to Obsidian's best (K2/MOTB) and away from its worst (NWN2 OC). And, for god's sake, more story adventures with more different outcomes/ skill checks / checking your previous C&C.