There should a tab in the shop for ascension mats, even 10 a month (or even a 1-time buy) would be good enough. That's enough to get a character to level 50, and that's all a new player realistically needs before they level up enough to even be able to level past that, and by then they can access all areas for ascension mats.
It's an oversight that shows that Mihoyo may not care that much about QoL changes for new players, but really, this problem feels mostly theoretical right now. It takes a while to get 75+ wishes, even as a new player, so they'd be making that change for 1% of new players who get lucky and get a 5* before pity (which is probably literally tens of people worldwide). As I recall, the starter rewards are mostly blue wishes, so you're not getting a new character from those. So by the time you actually get a limited banner character, chances are you will be AR30+ and can get to any area you need. It will get worse in time, but that is also probably the time Mihoyo will have to make those QoL changes.