The thing with the abs is that they depend, a whole lot more than other muscles, on the body fat percentage. If you carry just a tiny bit more fat than you should, bye-bye abs.
I actually don't train abs. Ever. Yet they look fine. But I do a lot of compound movements.
Would my abs look a little bit better if I trained them specifically? Yes. Would my abs look a whole lot better if I trained them specifically AND I took the necessary steps to reduce the fat percentage a little? Yes. But I don't wanna do that - the time I would use for abs is used for other muscles instead, and I prefer to follow a diet that allows me to make good progress in terms of strength and overall muscular mass.