1. Language is complicated. Speech is much easier.
We're talking about Rs and Ls here. Not major neurological rewiring.
I come across a lot of speech teachers...that is Speech-Language Pathologists (SLP). SLPs go through intense schooling to learn how to help people communicate. A lot of their focus is on language. Language is a complex beast that is hard to put a finger on. Speech is separate from language and is much more measurable and coachable.
With a little bit of work parents, even YOU, can help coach their child to pronounce difficult sounds. Sometimes there are underlying problems that need a professionals, but most parents know if something is off with their children and can tell if they need special assessment.