They are likely as wrong / right as simple games with which they are replaced.

Can be a good thing to help you wind down, if applied in moderation. Can waste your time otherwise. All non-trivial activities take some learning to do efficiently; thinking is no exception.

I think you’ll have to define the measure of correctness here as I don’t think I understand what right/wrong means at all in this context.

If we are talking about leisure time as understood by the subject, then it’s difficult to see how a non-harmful activity is a ‘waste’ of leisure time. You can’t waste leisure except by trying to get some sort of work done during leisure, I think.

Other than that, idle thoughts are a wellspring of creative ideas, leaps of deduction and what not. Games like bejewelled are not similar at all; in me, they quickly lead to obsessive hyper focus and a Tetris effect, which is why I don’t play them. But idle thoughts are quite the opposite experience.

Do you really think that sitting down watching the grass grow, clouds, bunnies playing... whatever, is actually a bad activity if done for an extended period?

If you have no responsibility that is being compromised, how can this be a bad thing or is time wasting?

You seem to be saying that everything you do needs to have some purpose or needs to be productive?

I suspect that the problem that society has is that we have decided that everybody needs to be productive and working towards something, even in recreation. Time to spin your wheels in an unstructured way is one of the great things about modern life. We don't have to be spending every minute of the day just trying to get our next meal.