Change is affected by numerous social forces, including education, mass media, and various other forms of social uniformatization. This can both retard and accelerate language change. For example, the widespread adoption of expressions ("sentences") like "As if", "whatevs" and so on would not have happened without mass communication gadgets. Central California vowel centralization has spread considerably over the past 30 years, for some social reason. There is a register often used by police department spokesmen which is similar to and attempts to emulate high register talk promulgated by standard education and propagated by the media, which surely would not exist if society were the way it was 200 years ago.
There is no issue of "allowing" English to evolve – no legislation or agency can directly force people to pronounce "which" differently from "witch", and no law can suppress the pronunciation "boid" for "bird" in New Orleans (and elsewhere). If it becomes socially disadvantageous to say "boid", then people may be motivated to change their pronunciation. "Boid" can also be a badge of yat solidarity, so it depends on one's goals.
Linguistic "suppression" is primarily manifested via dialect choice, as exemplified by the spread of Standard General American in the southern states (among those born in the south), since southern dialects are stigmatized in some circles. Since all linguistic change starts at a very localized level as a deviation from the current Standard Language norm, hindering a language change amounts to a language change failing to catch on sufficiently. This happens so often that we don't even notice it.