Musicals have always been a genre of film that has changed over time for a variety of reasons. The first reason is that music itself changes during the course of time, and in order for musicals to succeed, they, for the most part must be current.
This is of course unless you are doing a period piece, but even in this case, there are things that reflect the current state of music. Take for instance, the play Hamilton. While there is a historic context to it, the music is a blend of soul and hip hop, which was not necessarily in tune with how music is today.
The wonderful expansion
In addition to different more current styles bleeding through into historical pieces, there is now a more global artistic landscape in which lines become even more blurred. This is to say, that musicals, both old and new still feature an element of modern music.
Because there is such a global culture with the Internet, there is less of a divide between what we find musicals to be like in different countries. And while there are still many differences, there is much more commonality between the musicals from different countries.
As a large fan of both music and art as well as how the Internet has changed the world around us, I find it interesting that musicals have become much different in their content and presentation. It is a sign of how we as people are becoming more connected and that musicals are still a large part of how we live.