Are you suggesting that abstract classes are a good idea in TypeScript? Because to me, abstract classes suggest that you're doing a lot of inheritance, which is the opposite of a good idea in JS.
I'm not judging if the author did something right or wrong, but that he got "ridiculed" for doing something his coworkers judged wrong, and that he insults them back.
Why? Old-school pre-ES6 explicit prototype wrangling was confusing, but what's wrong with using inheritance if you're writing in TypeScript (or, for that matter, a JavaScript version with classes)?
Too much abstraction can be bad as well, many times I’ve written a nice class diagram to discover no one really needed to reuse certain functionality, a function would have sufficed :P
No, but "got ridiculed because apparently nobody does it this way" reflects poorly on the coworkers (or on the author's perception of the world), while "I certainly pretended that my colleagues were hopeless idiots" is also rather immature.
tl;dr: it sounds like a toxic work environment where everybody loses.
Author may have left out the part where his co-workers said, "no one does it this way [because it's usually a bad approach using this technology, and your particular use-case isn't some special case where over-engineered and brittle inheritance is actually a good idea.]"