Stuff is still being added nowadays: non-integer derivatives and integrals (”fractional calculus”), alternative formulations that rely not on the limit of the addition but on the limit of a multiplier (“L-calculus”), stochastic integration (Itō integrals), automatic differentiation (vital to estimating weights for neural networks in machine learning), derivatives of integers (???!!!!), and other things that might or might not be important going forward are all branches that have been developed since the 1960s.