I wouldn’t use it, simply because I would need to make a bet on this website existing for the rest of my life. Statistically, that’s unlikely.

Idea is great, however I probably have trust issues :)

As a tech person, I would probably create encrypted file on my family cloud drive with instructions, to be sure that I own the data and I know what happened there. On another hand, it requires some efforts (and also instructions for the family how it can be decrypted - the hardest part :D )

I do a yearly update of all important account details and passwords on a shared keepass. Then sit down annually to review it all.

Outside this i have encrypted drives and shared passwords on this

Also review wills and power of attorney every few years

There is no way I'd use a web site for this, partially because there is no guarantee the site will still be here in 2 years, much less 20+ years. But more importantly, I can store that info in any document online. I don't need a new web site for it. I can (and do) also store it with the attorney who holds my will. And my older family members have a printout in a file cabinet at their home where I know where to look.

Overall, this is not a tech problem. You are trying to use a web site to replace a communication gap with your family.