Are we looking at the same thing here...?
In the second shot (main panal back) your looking at 20-30 year old wireing, crimp connected on to a coroded metal strip with no insulation and a couple "newer" wires ran in and added on....
And for the most part your "OK" with that...?
In the first shot I think we're looking at new gauge backs with a factory made (probably robot) multi lead wire harness (large black wire) with factory "quick connects" to make your repower "plug and play" .... that's why it's not all "L" bent and labled...
The open access to the backs are also a 20-30 year old design issue and not part of the current install...
Right, after a closer look there is some green growing on the ground side terminal. Kind of hard to tell from the photo, but the basics may be able to be
re-furbished, assuming the wire, point to point, is sound.
An alternative, maybe not much more time consuming, would be to use the old wiring as pull wires and pull all new wire with proper terminal fittings,
maybe even a new breaker equipped panel. A bit of a job but well worth it in the end. Or, "if it works, it works", just leave it and pray.