Swapping specs is a necessary thing, though (although maybe not for a mage). Otherwise hybrids won’t have role flexibility when building pugs. “This group needs a tank but I’m stuck in Holy until tomorrow” wouldn’t be good.
I would be OK with some of the within-spec choices being stickier than they presently are and people just being expected to use the tools they have, but I think a lot of other people wouldn’t be - just look at all the complaints about Azerite respeccing.
If Blizzard had designed the talent system with a substantial CD when they rebuilt it in MoP we’d all be used to it by now. Even 1h would be enough to curb the most degenerate/immersion-destroying behaviors without stopping people from having a M+ build and a PVP build or w/e.
P.S. I don’t think trees vs. rows matters to this issue. Trees that you can swap in any rested area would just lead right back to where we are now, but with more clicking per respec.