I don't think it is quite true.
it is true that a couple of years ago (2010-2012 for example) you could mine bitcoin with your PC and when you found a block and got the reward or share of the reward because you were in a pool, that bitcoin was worth so little. for example $10-$20,...
but now if you get the reward or part of it, that bitcoin is worth $13000+
so saying before it was profitable and now it isn't is a little misleading. it still costs electricity but you will earn a lot more and if you hold part of it, price may go even higher and that can worth a lot more.