Nobody's suggested parenting a toddler like an 18-year-old 😂
What they're saying is that deep, critical emotional pathways are laid down in the early years. From the NSPCC:
The first two years of a child’s life are the most critical for forming attachments (Prior and Glaser, 2006)
During this period, children develop an ‘internal working model’ that shapes the way they view relationships and operate socially. This can affect their sense of trust in others, self-worth and their confidence interacting with others (Bowlby, 1997)
When caregivers react sensitively to ease their child’s distress and help them regulate their emotions, it has a positive impact on the child’s neurological, physiological and psychosocial development (Howe, 2011)
Children with secure attachments are more likely to develop emotional intelligence, good social skills and robust mental health (Howe, 2011)
... There's no suggestion that OP's little girl lacks nurturing, care, safety and listening from her adults. What people are trying to point out is that this early, nurturing environment is exactly when emotional self-regulation needs to be reinforced. The other part of this same process is teaching theory of mind (consideration for others), which won't be properly established for several more years but can and should be started at her age.