[zaarn]

Idunno, "Save as HTML..." seems to go for that dream pretty well. And lots of other sites utilize service workers fairly well to work offline.

[imtringued]

Save as HTML is often completely broken. Especially when javascript injects <script> tags to load even more javascript. You're better off by using archive.org's wayback machine.

[zaarn]

There is a number of other offline tools available (google "archive team warc ecosystem"), they just need better integration.