That's not how I read it. I think the guy wasn't "not making any effort to do [his] job", he was burnt out and tried to make the effort but failed.

His reply is not surprising from a Russian perspective (in broad strokes Russian discussion culture is extremely...let's say "honest", to the point of appearing crass or blunt to western ears) & does not mean "I don't give a shit as long as I get money".

I read it as "if you want to fire me, do so", and I don't think that's too bad (as in this case the appropriate response really is firing - not asking the guy to quit).