Keep in mind that the talent revamp isn't a small change by any means. It's not just the extra icons in the talent panel, it's the end of borrowed powers that we see ever since Legion while also reusing the ones that defined the spec at the time.
When you think about it, there was a major 'source of power' in every expansion except WoD. TBC introduced gems, WotLK introduced glyphs, Cata - specs, MoP - talent revamp, Legion and BFA - AP, SL - covenants and legendaries. It's just that the last 3 expansions had features that were forgotten after the next one was released, some were even a one-patch thing(corruptions

). This is what caused the community's disappointment and blizz are finally realizing that.
What the new talent system does is something that none of the previous expansions did - it combines previous powers into a single 'source of power'. Even though I haven't seen it complete, I think this is the right direction.