You can go talk to TC39 delegates in #tc39 on freenode right now (it will be kind of quiet for the next few days though since there is an in-person plenary and people are not looking at IRC as much). We also use https://es.discourse.group/ for async communication.

Also, many entities listed on Ecma's membership page are not there for TC39, and talking to people working for them will not get you anywhere.