I agree that generics should probably be a strong consideration right from the beginning. I disagree that this would mean that it would necessarily be done correctly or that it's impossible to add it later. That was the case with .Net and C#, it wasn't until the 2.0 release that generics were added. [0]

[0]: http://mattwarren.org/2018/03/02/How-generics-were-added-to-...