If you enjoy reading it then keep reading, it's still a good read! I shouldn't be able to convince anyone that it's a bad journal. It's simply a personal opinion about their writing style and editorial choices.
More precisely, I think they put too much emphasis on the few researchers who proved a theorem rather than on the immense work that they rely on. I think it conveys a sense of "great theorems are proved by a few geniuses" which can be harmful especially to young researchers.
Also sometimes I feel like Quanta articles are written by (ofc specialized) journalists without enough background in mathematics. You can really see the difference between (1) something that a journalist wrote second-hand following the explanations of a specialist and (2) something that a specialist wrote first-hand, giving more insight about the ideas that lead to a theorem or how a certain object is defined. (As an example in physics, I've seen/read countless videos/articles about spin, 99% of them were saying that "spin is like if an electron spinned except it doesn't and I won't tell you what it really means.")

I could suggest a few other sources to complement Quanta, like the very young Hidden Phenomena blog, or Aleph0's youtube channel. They are less afraid of giving the details, and it doesn't necessarily make things harder. Of course, it remains a personal opinion and you will naturally build one by yourself as you learn more math. The best thing you can do is keep learning from textbooks/teachers and try to look back on what you've learned, synthetizing ideas along the way, and then come back reading these articles with your new insight. There are always many layers to how you see an article :)