Is that from scratch? I'm using an i3 on a 1 Mbps satellite connection, and opening up Gmail now (having opened it earlier today), it was 0.27s until DOMContentLoaded and I could interact with it. It continued asynchronously loading stuff in the background but from my POV it loaded in 1/3 of a second, which in Chrome is faster than the app opens on my iPhone 7. I have disabled the Hangouts/Chat feature in settings which apparently makes a big difference.

Can you try in Guest Mode (or Incognito but only if you've disabled extensions in it)? I'm guessing you either have (1) battery power or other cause of downclocking, (2) slow extensions, (3) disabled/small cache, (4) an old CPU (old gen i7 maybe?), or (5) a large distance between you and the server. I have a similar machine to yours that's 3+ GHz and it's consistently loading in less than 4 seconds when I'm on AC.

(To be clear, I'm not excusing how slow their code is, just trying to help you save some time in the long run.)

Takes 2.5 seconds with Chrome on my Quad Core i7 (laptop)

Takes 2 seconds for me on a 2018 MBP