The point of breaking things into tiers is the criteria. That's why the 3rd edition tiers had defitions.Ok? It’s still the same concept, 3e just had a much greater power delta. You could easily just change the tier names to S and A-E instead of 1-6.
You can break anything up into tiers, 5e would just have a very narrow delta, with the difference between tiers being very small.
What criteria is being used here? If the power delta is very small than coming up with meaningful defintions to break things into tiers is correspondingly harder.
And if all we mean is better than other options than the concept of tiers isn't doing any work. It's just ranking.
I'm not quite sure what we're talking about here. If all we mean is that overall some subclasses are better than others then that seems inevitable that it would be so.
Is that the point here, to just discuss which subclasses are the best for each class?
Why not just say that in the first place then? That doesn't require any jargon.