Your are indeed! Many people like myself prefer the lightning fast interaction of keyboard navigation, the mastery of the bindings to improve workflows, and the customization of bindings to create new ones.
As with most web apps, it's more of a preview than an application.
You may not have to learn "new shortcuts" (they're pretty standard), but you're perfectly willing to learn an entire text-based configuration scheme?
VIM has its merits for _editing_ code, but that's not what you're doing with e-mails. You're usually just writing them and sending them off. It doesn't matter if you can save a few keystrokes to, say, change a word a few paragraphs back, and you're not producing structured text in any meaningful way.
It's perfectly fine to like the terminal, but you _have_ to admit it is a preference that has nothing to do with "efficiency".
For Yazi, I even created a hardcore Vim configuration that makes it even easier and more efficient for any user familiar with Vim keybindings.
Just one example: look at your email program. Perhaps you have a folder open with 100 emails. Now, imagine that each email is nothing more than a line of text. So, you have a document with 100 lines of text. In Aerc, I can simply jump to the first line (the first email) with `gg`. And with `G`, I can jump to the last email. With `ff`, I filter all emails that have the same sender. With `fs`, all that have the same subject. With `V`, I mark an email, and with `X` or `dd`, I can delete the email. Before that, I can mark all the emails I filtered with `G`. If I don't want to delete them but move them instead, I just press `pf` and enter the first letters of the desired folder where I want to move my emails. I can also set certain folders where I often move emails as shortcuts. For example, `pb` to move emails to the "Brain" folder. Have a look at my simple config: https://github.com/rafo/aerc-vim/blob/main/binds.conf
Once understood, everything becomes incredibly fast.
Tip: try surfingkeys in your browser.