Euron is Wildcard Charlie in pirate-king form and I don't think I'd have wanted to shoehorn him into enough showtime to flesh him out into a more complex character. Dude is different and it's fine. Likewise for Vargo Hoat/Locke.
Actually let's all be thankful that Vargo didn't make it in as an accurate portrayal.
Im not going to lie, I was a fan of Euron's character in show. He provided a good amount of comedic relief while still being a good 'villain'. I didnt need more of him on screen, but i dont think any of his scenes were necessarily 'wasteful' - or at least not the ones in my head. I suppose the conversation with Yara wasnt necessary, but i viewed that more as a setup for her release than a Euron moment.