Our company started out using Lightning but the more I use it, the more I realize that I have to learn to use Classic as well. Having to switch back and forth between the two is SO INEFFICIENT. Please make this a priority.
I created an entire series of email templates only to discover that none of them can be used in email alerts because they are lightning templates. This doesn't seem to be a big ask and it would go a long way in promoting lightning adoption.
Definitely needed feature, otherwise, we end up doing so much work around such as creating HTML template using enhanced email and letterhead which create an HTML code automatically and can copy in a classic email template to get the same look and feel for an email.