I think that’s largely a consequence of the 5e design in general. It doesn’t leave a lot of room, natively, for exciting challenges from its monsters. You’ve got to go to third parties, like Colville’s “action-oriented monsters”, or other systems like PF2, to get that.
The main thing missing compared to the 3.x version that would hinder the flying archer strategy is its regeneration and needing to use Wish or Miracle to keep it dead. Trolls and Vampires have conditional regeneration, Zombies have Undead Fortitude that gives them a chance not to die when reduced to 0 HP, the concepts were there they just chose not to implement them.
Fun fact, MCDM’s Flee Mortals! book has its own stand-in for Tarrasque - Goxomoc. Fool’s Gold: Into the Bellowing Wilds also has Dire Tarrasque
I’m a little sad that that book took so long to arrive that I had gone from never even considering moving to another system (other than for some fun temporary one-shots & small campaigns to add variety) to basically not being able to imagine myself choosing to go back to D&D at all, between the time I paid for it and when it finally arrived 5 months ago. Because I really did love the idea of it when it was being Kickstarted.
