The arguments about completely removing the plugins were always questionable. Yes they had security problems. Now the attack surface they represented has largely been moved to the browsers themselves, which also have security problems, often of a similar nature and for similar reasons. Plugins had stopped being a vehicle for drive-by downloads and the like thanks to better browser safeguards like click-to-play long before they were decisively removed.
Some of the most popular programming languages in the world behave significantly differently between major versions and have developed effective solutions to manage those differences. Sometimes those are as simple as a command line compiler flag or config file setting to specify a target language version. And of course the libraries used with many languages also frequently have to deal with complex dependency resolutions these days. I do not understand why JavaScript is special and could not adopt a similar model if the will was there.