This is true, the monstrosity I inherited at work is built on bootstrap (2...and it was started after 3 came out..)
but modern tooling has radically improved.
yarn/typescript and (though some days I hate it..it has gotten better) webpack largely make it feel sane(r).
That said getting to a point where I was comfortable with all three was insanely more complex and time consuming that picking up Delphi 6 was in the early 2000's.
Shrugs, the beast is what it is until someone does something better.