I think the value of the subclass is depending on the different base class. Lets take Barbarian for a moment. For the most part, no matter what path you end up taking, it starts to feel same-y. A Bear barbarian isn't really acting that different from a berserker, nor from a wolf barbarian. Sure, the wolf barbarian is going to stick closer to the party, and the eagle runs around more, but that's not really a major difference to me - its stuff a base barbarian would likely do anyways. Just some bonuses for some certain tactics. And, even then? Any barbarian will use those tactics if necessary.
Then, we look at the bard, who goes from gish to pure caster Pretty huge variance there. Druid who goes from shapeshifter to caster (at least level 2-11, at which point things break down). Well, that's just an issue if we're going to see more variance from these two options, though. Gish and pure caster - are we going to see actual meaningful differences in the future?
The wizard who, despite all subclasses having access to each spell, very deliberately has a different focus - blaster, undead army, summoner, buffer, etc. They all really play differently if you follow the spell types.
Some classes come off as vastly different, some come off as wildly variant. Some are in the middle.