Does high fantasy begin when someone can shatter time with their muscle strength? Because again, Lord of the Rings is high fantasy. If that is the lower bound then level 1 D&D 5E is already high fantasy if the DM makes the scales of the adventure epic. It's not what the PCs can do, it's what the game is about. The "high" in fantasy is something the DM decides, not the players and not the books.
If the lower bound of high fantasy is Goku exploding a planet with a ki-ball then D&D becomes high fantasy when the DM allows a 17th level wizard to use Wish consequence free.
Considering these goal posts are so far apart that you can't even see both of them the only way to answer this question is for the OP to define what they mean by high fantasy, since they're not using the conventional definition.