To name a few low-hanging fruit:
The research done to make it possible, would definitely advance several fields.
The ability to access photons from outside of the atmosphere should vastly improve how much energy we could capture from the sun. Pair this with transparent solar tech designed to pass through the wavelengths that are useful to plants, and we can factory farm crops in space using fully automated systems. This could also lead to exploration of engineered crops that can withstand (and potentially absorb radiation), that may serve as a biological wall for the humans.
Obviously, it would be a given that asteroid mining would become vastly more simplified, and autonomous robotic space construction and perhaps even asteroid mining would become a fantastic way to profit from it (or/and dilute the value of existing rare earth minerals/metals).
Obviously, this would also make intra-solar travel orders of magnitudes cheaper.
Maintaining and cleaning up space debris would become substantially simpler.
Building planetary defense mechanisms (against extinction level events) would become more feasible if we have this in place.
There are obviously an enormous number of things that could go wrong with a project like this, but given a CERN or Manhattan Project level of funding and cooperation, I think we could build this in a couple decades.
This is the kind of future I would want to be a part of. The cost estimate I think was somewhere in the trillions, but even so, the potential benefits are so vast that it just doesn't make sense not to do it, right?
In case you don't want to google the wiki page: https://en.wikipedia.org/wiki/Orbital_ring
Don't even take my word for it. Go question ChatGPT about it.