will sharepoint ever have built-in conditional visibility dropdown?

yes, it is there but not easy to find. Open the view/edit form for an individual list entry by double clicking on it. In the top right hand corner you have an Edit Form icon with three options. Within the Edit Columns you will see a list, and then there is ... when you hover on the right hand side of the column name. Within there is a conditional formatting for visibility. This is the help page: https://docs.microsoft.com/en-us/sharepoint/dev/declarative-customization/list-form-conditional-show-hide#specify-conditional-formula-to-show-or-hide-columns

Hi

I believe it already has that as you can do it via JSON formatting. where conditional is a menu item. Check it out via column formatting