I'm fine with little UI tweaks. I'm not a fan of how the UI is becoming "flatter" with every release, and I wish they had toggles for some of the more questionable features (like those recipient bubbles which can't be easily edited, or the absolutely inane treatment of TO/CC/BCC).

If you don't want your software to change, don't update it. The way Thunderbird looks and the messages list is a large part of it is horrendous and is a deal breaker for me, for example.

> don't update it

It is an application that receives content from the Internet, your advice is dreadful. Email is a primary vector for exploitation.

Correct. And also customer needs, UI technologies, the way people use apps and services change. So it's all right for apps to change as well.

It's alright if the UI isn't made worse.

The modern example of fuckhead UI changes. Changing settings without having to click apply and/or OK. Changing from the "cog" icon to those three idiotic bars (hamburger?).

Interfaces are often used by people who are not IT savvy. The simplest of UI changes can mess their decade(s) old patterns of usage, the elderly are the easiest example of users affected by this. It not just their individual problem, those people then reach out for help which can be at considerable personal financial expense.

Shouldn't mailservers and desktop AV be doing the heavy lifting on this front and blocking known exploits?

For your purposes I'll keep it simple and just say "about 99.9% yes". Trust the word of a seasoned veteran - keep email clients, browsers and OSes up to date.

I really do pray that this "modern", "flat" craze is just a fad.

I dream of a future when normal interfaces and drop-down menus return.

How about an option? Just like the new UI changes, they're all configurable, and ultimately if you don't want to use them, you don't have to.