As a corollary I'd like to say: stop pushing JavaScript forward. There seems to be a lot of focus on providing syntactic sugar for things that already exist (like classes, decorators, etc) at the expense of flexibility and composability (executable class bodies, @foo vs normal function application, etc).

What JavaScript needs much more IMO is a (better) stdlib, with more datatypes and procedures than currently available (including big numbers, the various flavours of trees, better support for equality and comparison, etc).