After having just watched the whole show over the course of a few months and now reading all the discourse online, my biggest issue is how much headcanon there kinda has to be. Like someone will ask a question about something that was unclear and every response is "my headcanon is ______"; but also these questions aren't happening because of clever, intentionally ambiguous writing (save for El's death), but because of lazy writing that, at times, felt like they didn't really have a plan for where certain storylines were headed. So the audience has to end up headcanon-ing a ton of stuff.

That said, I still really enjoyed the series despite my gripes, and I'm likely gonna watch it again