Merkle Hash Trees are not a solution for offline checks. You can very easily check membership in a tree if someone sends you a proof of membership. But to get a proof, you'd either have to generate it yourself (meaning you're storing the whole set anyway) or get it from a third party (ie an online lookup, which is what OCSP is). The forefront of CRL design is in set compression techniques like Ribbon filters https://arxiv.org/pdf/2103.02515.pdf