It's not clear to me Caemlyn was removed in favor of Tar Valon to show Moiraine and Siuan as lovers. Rather, the issue there seems to be practical. You can't put in all the money to build a big city, and the sets for the Royal Palace, for one scene in season 1, then leave it dormant till whenever book 6's story comes to screen, because that's when this set becomes useful.
Same with the actors. They already lost the guy they hired for Ingtar, and have to reintroduce him again in season 2. If they hired a Morgase, Elaida, Elayne, Gawyn for one scene... And one or all quit because they got juicier roles elsewhere, you need to change actors,.which gets confusing. Of course, they ended up having to do that for the actor for Mat due to the pandemic anyway, but that just emphasizes the risk.
I think that's why ascribing the awfulness of the show purely to their decisions to update some aspects of the books is unsupported. They're both in the hands of the same creative team, but beyond that, there's no causal connection.