I know how you feel. Gmail's interface has become incredibly complicated and every change feels like a step backward.
But as much as I don't care for Gmail's current interface, I can't and don't expect Google to support older web interfaces. If I really wanted interface consistency, I would run my own mail client.
That's exactly why I do run completely own servers, email, website, private communication platform etc. I don't like Google at all. Using Gmail is a trap, as we have seen here in other discussions.
I don't use Gmail or other Google services either, but that has nothing to do with their UI; it has to do with me not trusting them with their data. You don't need to use Gmail's web interface to use Gmail; you can access it using any IMAP-capable email client.
But as much as I don't care for Gmail's current interface, I can't and don't expect Google to support older web interfaces. If I really wanted interface consistency, I would run my own mail client.