Welcome to the forum. I have moved your post to an existing relevant thread. If you have a look at the preceding posts you may find relevant information.
I had old black solar matting and it heated the pool fine for a long time (see post #6 above), so the failure to achieve acceptable temps may be a function of where you live, or possibly being not the optimal orientation, or shading. Where are you located?
I can’t advise what blanket to buy, but I can advise you NOT to buy a Daisy Pool Cover. The cover was perishing in a relatively short time, and Daisy did their best to obviate their responsibilities under the ACL. See Solar Pool Blanket Issues. We did buy a new Daisy cover and it has lasted better, but I would not buy from them again.
