That's kind of the point. Ask yourself: which people would you genuinely be excited to make a little happier? (through a compliment or otherwise) Whose opinion are you keen to carefully listen to and consider? Who do you like enough such that you will want to put in the effort to remember their name?

I think the idea is that if the stranger on the bus has a haircut you genuinely find to be wonderful: tell them about it. You don't need to force yourself to be nice, just take action on the things you're genuinely excited to do.

And if you don't ever want to be nice to people, then you have some digging and reflection to do (including about if/when you are nice to yourself).

Well, force yourself to care.

I'd argue that there is a very strong value in doing something good, not just because it's genetically or socially imprinted on you, but because you actually decide to do it.

This applies to everything, there is no merit in being good at something just because you were born that way.

I’m not so hung up on the semantics. The fact that you’ll likely never meet someone again can render an act of kindness towards them, no matter how small, more meaningful, not less.