https://www.quora.com/Can-all-of-theoretical-physics-today-be-cast-in-the-language-of-differential-geometry-Is-this-useful-or-necessary-Is-the-modern-form-a-tensor-notation-or-differential-forms-or-other-What-are-some-book/answer/Paige-Brady-24
I’m no expert yet, but as someone interested in studying condensed matter theory and pursuing a math minor, I have been advised several times by mathematicians and physicists to take courses such as Euclidean Geometry and Topology. A decent number of graduate-level theorists at my school finish their research in the math department under the advisement of professors who use geometry in higher dimensions to solve important problems relating to theoretical physics.
So, certainly not all, but a fair amount of modern theoretical physics research requires differential geometry. Again, I’m no expert. I can only say that I am personally going to be using this in my research, and I know a lot of students and professors in physics who also do. Outside of my department at my school, I don’t know if it’s accurate to say that ALL theoretical physics can be cast in the language of differential geometry. I hope that helps.
Edit: I did not actually use differential geometry in my undergrad research, so you can take whatever you want from that.