> Also, for both large and small-scale projects, is it viable to forego front-end frameworks and rely solely on HTML, JS, and CSS?
Yes, as long as you are willing to establish your own "framework" if you need to collaborate with others. I've personally found the trickiest part is keeping common HTML fragments and CSS standardized across the site. If you can get it down to a common Layout.html, Navigation.html and Site.css, you will probably be able to manage the complexity in a reasonably-sized team. If you need to edit one of these common files, convene a meeting. Everything else is an independent partial with its own HTML/CSS/JS.
The hardest part is learning how to do everything in direct terms. MDN is your bible for this mission.