I don't think it's just us getting old. Newcomers to the filed don't really understand HTML and CSS. It's just "React components" to them, and they aren't looking deeper than that.
I'm getting the feeling that a lot of old timers also don't understand HTML and CSS in emails, from the responses I'm seeing here.
There are a lot of reasons to have abstractions over HTML/CSS in emails, for all but the trivial cases. It is notoriously difficult to get right, since there are some features lacking and standards in the email client space moves way slower than browser.
A regular marketing HTML email would look unrecognizable to a lot of old timers.
That's pretty unfair. It doesn't look like an html page they'd create for the web but I'm pretty sure they'd recognize html and css. Would someone who templated it in react see the connection?
As long as you stick to only HTML that was available in the year 2000, and use zero CSS, your mails will come out the same in pretty much every client.