Unless I am misunderstanding, you are suggesting that a new reader should judge a book by its cover- I agree that there are tons of great books which are unknown and might be passed over, but one could spend years of thier life reading well known, much loved, critically acclaimed books and still not run out of material - so whats the point of taking a chance of something obscure (and possibly a dud) if you are new to reading?
I am suggesting they select a book based on what appeals to them, mainly by using the blurb on the back cover or front flap. I am not suggesting they judge a book by its cover alone, though that is a common method of selection by both new readers and seasoned readers.
You make a good point about there being a lifetime's worth of reading critically acclaimed books, but I think most people, especially before the internet became so ubiquitous, selected books in a manner similar to the one I suggested. New readers included. It's worked well enough, I'd say. It's certainly worked for me.
I also suggested it because I do not know who this person is or what they like. I don't know if they prefer epic fantasy or romantic fantasy, Bildungsroman fantasy or historical fantasy. I don't know if they prefer female leads or male. Adult or juvenile. See what I'm saying? For every book someone loves, another person hates, so recommending popular titles might be helpful, but it might also not be.
The Lord of the Rings is a well known, much loved, critically acclaimed book that many fantasy lovers can't stand reading.
For someone new to reading, I would suggest they find what they like and not feel pressure to like what is popular or highly regarded. In a way, giving someone new to reading a critically acclaimed book can backfire if they dislike it. They might feel that if that is one of the best the genre has to offer, maybe the genre isn't for them.
Either way, there are of course alternative ways of finding books, but I hesitate to say better (or worse). Different ways work for different people. If this way doesn't work for you it doesn't lessen how well it works for me, and possibly others.