Putting dummies, autism and lockdown aside...
I was hanging the washing out this morning, with the 15 month old sitting on the patio next to me. They were babbling away, showing me bits of grass and stuff they'd found, pausing for my reply and we had a very nice little conversation. I have absolutely no clue what they were trying to tell me, but it didn't stop me replying and speaking back to them in full sentences.
I've never felt weird doing that with my babies or, before they began babbling, just narrating what I'm doing to them and engaging with them. When they started speaking I always made the effort to try to understand what they were saying, even if they couldn't make all the right sounds, it used to pain me to hear friends just say "riiiight, okay" to their kids when it was obvious they'd said proper words just a bit wrong.
It strikes me that Soph is exactly the sort of person who won't engage a baby or toddler in conversation as she thinks they aren't speaking proper words back to there's no point. Similarly, I imagine she's very much like friends I mentioned above who, if they don't hear a crystal clear word, just dismiss it as unintelligible sounds and don't try to understand what their kids are saying.
I'm not saying she's wholly to blame as there may well be underlying neurological or physiological reasons for Ron's speech delay. It's just something that popped into my head earlier.