Hmmm, it's really interesting seeing what different people think makes a 'great' song.
For example, Max Martin's hit after hit after hit does not make him a great songwriter in my opinion. It doesn't make him a bad one either. It makes him a highly successful producer with access to in-demand performers who are a crucial part of the success he enjoys. I won't pretend I know many of his songs, but I don't consider them 'great'. They're repetitive, predictable and somewhat insipid - in my opinion at any rate.
Mr Blobby was a massive hit, but I think we can all agree, it's not a great song. Are there great writers who've had no hits? I would say so, but I'm working from a different definition of 'great' to some of you.
I think what STC is noticing is that there's an absence of a more 'developed' kind of songwriting these days, including more interesting harmonic progressions, less repetition and a few more surprises. More Steely Dan and less Ed Sheeran I suppose.