For virtually any kind of art newer artworks will be on average worse than _surviving_ older artworks: the older artworks have undergone a selection process that weeded out the less popular ones.
This is IMO a more fundamental problem with any comparisons across long time intervals.
It's not because it's a popular show. It's just that people who didn't like the first few episodes have already stopped watching! And it's polarizing enough that the only people who stick around for so many seasons are the ones really love it. So it will get rated a 10 even for mediocre content.
But I came to the same conclusion as the op comment. Music can't really be judged by any one metric! But that doesn't mean that you don't gain insight into how music has evolved!
also, I did release my entire lyrics dataset that I scraped (about 500k) for free.
Yes, assuming you can find all the old chart toppers (and that this term has a consistent meaning over the whole time interval you're looking at). If, understandably, you have some gaps in old chart toppers, you need to assume something about them (probably that they were worse than all surviving ones, which helps if you're doing percentile-based comparisons).
This is IMO a more fundamental problem with any comparisons across long time intervals.