"Dropping old-school theme options means a lot less code work for developers, allowing them to focus more on styling."

This.

I wonder if one of the main reasons for theme authors not being so quick to adopt the blocks system is a perceived slow user takeup?
When users expect blocks and patterns, developers will provide them, but we need developers to provide block based themes for users to use them.

It will reach a tipping point where theme options as we know them will be the old way. Articles like this are helping to nudge it in the right direction.