I think the Kree/Skrull thing is a factor. A MCU Hulkling would be so different from the comicbook counterpart to the point you might as well just make him a new character. I don't like it at all, but I get why they'd go with Skaar if that's the plan. And let me repeat myself, I don't like it at all. Teddy/Hulkling is one of the most iconic and successful YA members. He's the flipping king of space.
Beating a dead horse here but Teddy should have ditched the "Hulkling" name years ago for obvious reasons. But even so it would be hard to make him a Mar-Vell legacy for a number of reasons in the MCU.