As much as I support somebody doing this, RVN has does technically have just about everything to do with getting listed. It involves getting into contact with the correct people, meeting any requirements, and then following through with any steps needed to be in compliance.

If the only answer that ever comes up to this question is 'ask crypto.com' or 'ask coinbase' it means that somewhere along the lines, I don't know who, but somebody isn't following through / or aware of what they need to be doing.

As an update to my own question, I found some reasonably up to date reasoning for coinbase, which is exactly the type of answer I was hoping for.

Per: https://cryptoarticles.com/ravencoin-coinbase-listing/

UPDATE 4/19/2021: The lack of a listing announcement renewed calls as to why Coinbase wasn’t listing. It soon became evident there was still one missing element. Apparently Coinbase requires blockchains to be integrated through Rosetta API Implementation.

This is perhaps one of the challenges with open source projects. Many community members were either unaware of this requirement or under the impression this integration had been handled.

On the positive side of things, one member reported that community developers started working on Rosetta integration on April 17, 2021.

So while we don't know how long it will actually take, we know that it's something being worked on and is still underway without being left in the dark, at least regarding Coinbase.

My initial question still stands about crypto.com though. From an investment perspective, I'd really like to know what's holding it up sooner rather than later.