I always wondered why ASN.1 never really seemed to take off. Tooling maybe?

Yes - both the protocol and tooling are expensive to support, even by 90s standards. Unless you have to use it for compatibility with a service you can’t fix it’d be much better to start with a better implementation of the concept.

ASN.1 has a number of problems with equivalent parsings (very bad in a security context, has been the source of a number of TLS vulnerabilities), as well as the fact that even discovering if two ASN.1 parsers will give the same result is undecidable.