I'd agree with your point about getting better as you go along because interviewing is a difficult skill to do well except for two things:
1 - She's had nearly two years since announcing the podcast deal to practice, train, do dummy runs, get feedback, practice some more and improve. She had the whole 2020/21 pandemic year where she could have studied the subject she wants to talk about and get remote degree/qualification in it so that she has a bit of substance to her interviewing... and
2 - It was a recorded and heavily edited interview, not a live one, with 28 people, including eight executive producers, six other producers, four senior engineers, two technical directors and a music supervisor! It wasn't Meghan giving a bit of interviewing a go on her own in a vacuum. What we got was either
a) exactly what Meghan and her producers wanted it to be (mostly about her and not her guest) or
b) it's the best few edited segments with as much of Serena talking as was usable.