I think my issue is that there are some very deep topics (e.g. cryptography) that require a lot of work to understand, including knowledge in tangential fields

I think my issue is that there are some very deep topics (e.g. cryptography) that require a lot of work to understand, including knowledge in tangential fields (e.g. number theory). It's a big decision to decide whether to go all-in and potentially lose years working towards something