Barriers have little to do with this meta or the last one for that matter.
Dive was popular because dive was relatively lacking in counters and dive heroes allow for taking, holding, and regaining important high ground (and Overwatch maps have a lot of high ground). Snipers aren’t popular because of anything to do with barriers, they’re popular because dive heroes aren’t in a great spot right now. Playing for ults is a thing because that’s what Zarya-based team comps do and it’s easy to play for ult with Zarya just spamming right click and Hanzo farming tanks.