As I build with progressive enhancement, ignoring the new pointlessly redundant HTML 5 "strutural" tag asshattery (aka the ignorant halfwitted useless section, article, aside, main, header, footer, nav), my pages gracefully degrade as USABLE in legacy IE in most cases.
Much of this stems from that when I build my layout I start with legacy desktop as my baseline for screen media. All the people saying "mobile first" have it COMPLETELY backwards since small screen is what we CAN target with media queries for changes. What can't we target? Legacy desktop IE... So that's the obvious and logical starting point. Start with what doesn't have media queries FIRST, using layout techniques you know work for that.
That starting layout should be elastic (built in EM not px), dynamic (containers adjust to fit the content, so no fixed height declarations), and semi-fluid (having a max-width so long lines aren't hard to follow). For really old IE that can't do max-width, if you care about that far back THEN you throw a fixed width at it -- in EM so at least it's elastic.
THEN you can use fancy CSS3 stuff to enhance the appearance. Legacy browsers don't get rounded corners, drop-shadows, or flex behaviors? OH HUFFING WELL!!! Seriously, don't bend over backwards for that artsy fartsy BS if the page is at least USABLE. AGAIN as I'm always saying people don't visit websites for your goofy layout tricks, goofy script kiddie BS, or goofy nonsense some artist wants to hang around the content; they visit FOR the content.
THEN you shrink the window, when the layout breaks figure out how many EM that is, give yourself a 5% extra as a buffer to account for different font rendering engines and behaviors, and that's your first media query. Lather, rinse, repeat until you're down to a single column of minimal padding. DONE!
Of course this is why you design in the CSS not some goofy half-assed overglorified paint program like Photoshop. ANYONE telling you that Photoslop, Gimp, whatever are "design tools" doesn't know enough about websites to be designing a blasted thing!
AGAIN, progressive enhancement. You start with your content or a reasonable facsimile of future content and organize it in a flat text editor so that it makes sense as if HTML and CSS didn't even EXIST. THEN you apply markup to say what things are, NOT what they look like. THEN you apply your layout CSS for legacy desktop adding semantically neutral tags (div, span) where and only as needed. THEN you shrink the window testing for media query creation. THEN you hang any extra graphics and appearance tweaks on the working layout. THEN you consider applying JavaScript to enhance the working site if desired.
You do that, the page will gracefully degrade in a useful manner as any fancy bits of the process -- like JavaScript, like CSS3, like all CSS and layout -- are missing, blocked, or otherwise unavailable/inapplicable.
Vary from that, and you probably have little if any business building websites. That goes double if you start out "designing" in a paint program like Photoslop, TRIPLE if you are building websites that work scripting only.... at least if you care about accessibility, usability, and speed.