I would say a few warp points are fine. As long as the game is not being designed around fast travel - usually a problem with games that are way too big for their own good and forego a tightly designed map. It's fine as a matter of convenience, but I don't think a Metroidvania game should be designed with the expectation that everyone will use it. Make your map a good size and make it fun to get around and explore in it first and foremost would be my recommendation. Fast travel is fine IMO, but I've always seen it as a concession for games that are designed to be extremely large and boring to get around in.
Sometimes just giving the option is enough. I don't ever go into a game saying "I'm not going to use fast travel". I know forsure if it was in the game I wouldn't have hesitated to use it and would have mainlined the game in 5 hours. When it's not an option you're forced to explore, get sidetracked, organically stumble across things you couldn't access before on your way to the next area, which I really enjoyed.
We can agree to disagree, but my point is that there's value in not including fast travel in this type of game, at least in actual meat of the game and not a potential postgame or newgame+ mode.