I think PNG is a good format even today. It’s lossless compressed, so there isn’t that much you can squeeze out of that with new algorithms as you can out of lossy formats with new and smarter approaches.
Sadly, PNG is being terribly misused on the internet too. What it’s good for is simple drawn graphics, which it can compress to oblivion. So it’s perfect for screenshots of say, your operating system’s windows. I took a sshot as I’m typing this, and it came out as 190 kB. Not bad.
But what it’s so commonly used for, is people taking screenshots of photos such as from Instagram, and then reposting them. So instead of a tiny and shitty 50 kB IG picture, you get a 1.5MB PNG screenshots. Some then recompress it to a 1.5MB JPG for “maximum quality” when they realise they can’t upload PNG to photo sites.
I also very often encounter huge PNG photos with their extensions changed to JPG, and I don’t know how or why that is happening.