The main mechanics have stayed remarkably the same for all 3 Borderlands games that have spanned 10 years. In other franchises, there are usually big differences from one game to the next. E.g. Fallout 1 & 2, 3, and 4 barely resemble one another.
I was able to jump into Wasteland 3 without a hitch, having recently played 2.
They're a lot of fun, these games. Lots of silly humour mixed with some decent combat requiring tactics and some planning.