Web developer here.
If your site has a lot of interactivity, it is a web app.
A read-only site like Wikipedia is not a web app.
A store page is not a web app.
Your bank’s customer portal is a web app.
Facebook, Lemmy, Reddit, Twitter, etc. are web apps because they provide a lot of interactivity.
I agree that the line between web apps and websites is blurry, but my thinking is if a website is built mostly using front-end technologies, it is a web app, if it’s built mostly with JSP or PHP, it’s a website. Things like the WordPress admin panel blur the line between the two as they offer lots of interactivity, but is mostly PHP-based.
Also a web developer. I don’t understand the reason you’d even need a common term to distinguish between the two. Wikipedia and Facebook are websites. Tons of websites have interactivity. It’s a spectrum. Why can’t we just say “website”?
