Anecdata FWIW: I upgraded directly from a 2014 (same keyboard as 2015 that everyone praises) to the first 16". I did notice a difference at first but adjusted within less than a week, never had any complaints after that.
My own anectada: I owned a 2015. It now belongs to my son. I also own a 16" with a Magic Keyboard. I had a butterfly along the way that was a total nightmare.
Going from the butterfly to the Magic felt absolutely incredible. I now own an M1 MacBook Air (mainly for the better and quieter performace, and the lack of TouchBar), and its keyboard feels about the same as the 16", so pretty good.
After a long time, I was helping my son with stuff on the computer, and as soon as I typed a couple words I was blown away by his keyboard. It's better in every aspect to the newer ones.
Magic Keyboard ranges from good to very good. The 2015's is superb.
I gifted my other old 2013 which had the same pre-butterfly keyboard, erased my data after I had already gotten used to the 2019. I did notice the difference in key travel then. But it didn’t bother me when I went back to the 2019 after. I honestly couldn’t say I’d prefer one over the other, besides current familiarity/muscle memory.
