When comments like this pop up I always think ‘thank god you joined the world fully formed age 25, and no one every had to wipe your backside or listen to you chatter’
Me too. Same with learner drivers, where some people who were once in the exact same position as they were will curse them with every name under the sun, just because they're a bit slower and more cautious.
The toddler stage can be challenging and noisy, but it's crucial for parents to engage with them. I'd a million times rather hear a giggling chattering toddler being interacted with by a loving parent rather than one who's ignored, shoved out of the parents' way and told to STFU every time they open their mouth.
Even if you don't care about the child and their family themselves, surely you realise that these are the kind of toddlers who are far more likely to grow up and be pleasant, helpful members of the community rather than the sort who make your life and neighbourhood a nightmare by seeking any kind of attention - because they never received it through the proper channels as they were growing up.
Essentially, you're asking:
There's a toddler behaving like a toddler - AIBU?
The toddler's parents are bringing her up with care and kindness, so that she feels loved, secure and valued - AIBU?
Sorry, YABVVVU.