What is "modern"?
Modern is just currentness. I'm being semantical now, but any "now" will always be considered "modern time"
Will we lose our progress, and revert to a stone-age level of civilization - globally?
It would have to be global, because there are hunter-gatherer humans sharing the world with us as of this very moment, so, humanity - as a whole - is not high-tech. Some communities live like in the stone age (
https://en.wikipedia.org/wiki/Sentinelese_people for example)
It would take a really serious disaster to throw all of humanity back to no-clothes and stone-tip spears
Even primitive societies are able to work simple metals, using ceramics and fire (you don't really need more. That is how stone-age society came to work metal in the first place: Ceramic (clay) containers can hold molten metal, and then all you need is a brick oven and some fire. A spear-mold, again, in ceramics, pour it in, and voila - you have a copper bronze spear tip. Alchemy!)
Ramble aside - I find it very unlikely that humanity would collectively be thrown back, everyone together, to such a state of existence, forgetting all our methods of refinement, forgetting all our written history - simultaneously - and suddenly finding ourselves at a stage where we cannot fathom how to weave clothes or tame animals
Like a lot of philosophical questions, it's fun to explore in fiction, but in reality we are more likely to persist like a bothersome infection, keep multiplying, keep developing, and we can only guess how far we will make it. Millions of years of further existence is not unlikely.
I do however suspect more barbarism, if that counts. As humanity continues to grow - exponentially at that, and a lot of world markets today allready base themselves in exploitation, this has the possibility of becoming more "outright" as the masses become more vast, and the individuals disappear yet more. People living as "modern slaves" count in the many millions, while in a less-than-ideal future, this could end up forming a larger and larger percentage of humanity. We have always predated on each others, and it seems like we are only going to continue.