This sentence doesn't make any sense.
"Mainstream" means used alot - widespread acceptance.
Lisp is #33 on Tiobe after Cobol, Foxpro, Fortran and Ada. How you can compare that to the takeup of the latest JS nframeworks I don't really understand.
https://www.tiobe.com/tiobe-index/
21 SAS 1.372%
22 Dart 1.306%
23 D 1.103%
24 Transact-SQL 1.075%
25 ABAP 1.065%
26 COBOL 1.055%
27 (Visual) FoxPro 0.932%
28 Scala 0.923%
29 Fortran 0.879%
30 Ada 0.787%
31 Crystal 0.756%
32 Erlang 0.733%
33 Lisp 0.690%
34 Awk 0.662%
35 Lua 0.648%
The reason those rankings are (mostly) useless is that it's based on search engine hits. An active, effective community that for whatever reason doesn't generate a million and one blog entries a month will not perform as well on the index. This makes it very useful for indicating fads in programming, but not reality.
Eventually some of these ideas will get dislodged and fall down to us, but you can't rely on that. If you read about Lisp's history it's very obvious why it is rejected by people at the moment.