The chain is much harder to do at higher difficulty levels, at level, than most other chains.

Getting into a PUG where anyone actually knows what's going on, or will take the time to guide newbies is so unlikely as to encourage people to claim it's impossible.

Once you get past 20, you're not illegible for most LFMs.

Unless you belong to a guild that likes to do ToD runs and actively helps flag their guild mates, you're unlikely to get help getting anywhere in the chain if you're new to it.

There's no real mystery. If you can't find parties for something, it's usually because it's just not fun, or offers nothing most people want.