On the other hand, when a subclass requires you to make choices to best utilize it before you get it, that's at least somewhat problematic. For example, let's say you're destined to become a dragon sorcerer. You better not take Mage Armor for the first two levels, because you're going to get natural armor! Oh and also, you need to focus on certain types of damage because you're eventually going to get bonus damage! And you have to avoid taking any spell that you'll get from your subclass, which in the case of the Sorcerer, means Alter Self, Chromatic Orb, Command, and Dragon's Breath.
I remember having a similar problem in Pathfinder 1e, where I couldn't take Burning Hands, despite having bonuses for using it, because I was going to get it for free at level 3.
And sure, yeah, you can swap out spells at level up in 5e, but you can only do one at a time, and it's still just unnecessary.
Is this as bad as waiting to find out at level 3 that you can wear heavy armor like in 2014? I don't know, but it feels like if your subclass is going to be transformative in any way, they should come in as soon as possible.
It also kind of feels a bit nonsensical that you get several features at once at level 3 out of the blue. What should be happening is that you should be getting these gradually. Like, why can't you get 1 thing at each of levels 1-3, to show you slowly becoming a "true" member of your subclass?
I feel like that would be more logical, but YMMV.