Alternatively one can consider that fast adoption driven by marketing isn't a sign of best quality. Take a look at Java.
I do like the verboseness, though, espectially for inheriting code.
Or is your point that JS took off despite that, and so maybe is high quality? I think that's wrong too.
Launched by Netscape with Sun approval (they used to own the trademark, now it is Oracle) in 95.
Netscape had money and marketshare.
It was adopted by competing browsers (IE in 96, Opera end of 97) and removed alternatives (perl, tcl, python in browsers (eg https://www.foo.be/docs/tpj/issues/vol2_3/tpj0203-0004.html ))
JS was a quickly made (in 10 days). It showed.