I dropped pinboard.in recently. The interface hasn't had improvements in years, the extensions are all third party, and the API if you wanted to build your own is pretty limiting. The mobile interface is pretty poor too.

I'm now moved over the Raindrop.io[1], which is another solo-developer outfit, but has had a lot of work put into it. It does all the same stuff Pinboard does (including page archiving but beside the social and public directory things... which nobody uses), but has a bunch of additional features. It has a much more complete API, a well maintained extension, and mobile apps! Definitely worth giving a go.

[1]: https://raindrop.io/