> potentially even allowing functions to become small enough that they can be inlined

Apparently, that's no longer the case, at least in V8[0]

Parse times however are indeed a real concern and start to matter a lot as you go down the list of mobile hardware and their performance. This graph[1] shows parse times for a 1MB bundle of JavaScript in various devices.

[0] https://github.com/v8/v8/commit/0702ea3000df8235c8bfcf1e99a9...

[1] https://miro.medium.com/max/1400/1*dnhO1M_zlmAhvtQY_7tZmA.jp...