My keyboard replacement program experience
I purchased my MacBook 12 in (2016) second hand about 3 months ago. I liked it however I found the keyboard very exhausting to type on. If I ever had to write more than a sentence, it would feel like a chore.
I took in my MacBook to the Apple store and asked if they would replace the keyboard to the 2017 keyboard. They did their typical scan to see if it was eligible. Then they checked the keyboard and said the buttons indeed feel mushy and unresponsive. So they agreed to replace the keyboard.
The asked me to sign and provide the password to the MacBook which I felt kinda iffy about since they could figure out my other passwords through Apple keychain.
TL-DR: if you have a 12 in MacBook from 2015 or 2016, you should take it to the Apple store and see if you can get it replaced to the 2017 keyboard (2nd gen butterfly keyboard) which is better. It takes 5-7 business days to replace they said.