[twmb]

Try the Basic HTML view linked at the bottom of https://support.google.com/mail/answer/15049.

It's is web 1.0, but it sticks, and it is fast.

[catacombs]

I have tried that, but Gmail forces me back to use the new interface.

[codeulike]

You can bookmark the html version. Also whenever main gmail is loading, there is a link to load the html version in the corner.

[ProAm]

You can set it as the default and it should save.