There are already procedures for an executor or heir to assume control of a deceased's financial accounts and assets, and part of that process is determining what accounts the deceased had.. You don't need to dig through Dad's Gmail for that.
Like the first poster said, anything actually important either already has procedures in place or will be figured out in the probate process or otherwise.
Trawling through browser histories and correspondence is often the only way to get a reliable picture of what's going on.
Last year's tax return will probably identify any significant investments, at least those that are producing income.
I, along with 95% of the world's population, do not live in a place where Equifax exists.
Tax returns capture some things. They also don't get filed for several years sometimes. They don't capture assets like cryptocurrency or off market shares.
Life is messy and death more so.
But you probably do live in a place with probate laws. This isn't a new problem, and there are processes to deal with it.