Right?
Something this old is going to be power inefficient compared to newer stuff, and simply not perform as well.
I would know, I just booted up a 10 year old consumer router last night, because the current one died. It’ll be OK for a few days until I can get a replacement. Boy, is this thing slow.
The problem is dealing with the application side.
Just one feature that’s massive - how many systems have automatic import/export using Excel file formats. Converting those processes will be a huge undertaking themselves, let alone how many other things that will require re-engineering. The scope and scale of this is staggering.
A better effort would be to convert a single, small organization in government, then the scope is limited, but you get to build the fundamentals, and gain the experience of interfacing with extant systems.