LOL -- yes, the armchair parenting is fun. It's so easy to know the correct way for someone else to parent
Remembering back to when my boys were toddlers, one of the books we had explained that personality-wise, there were four categories of toddlers: angels, angels most of the time, angels when kept under control but can easily become devils, and devils. The parents of angels could never understand the children who were devils, and tended to blame poor parenting, when there's a small (but extremely visible in public) set of toddlers that just don't do what they're told. They'll grow out of it and learn some self-control, but it's just the way they are. Most toddlers are in the second category, with the third category being the largest. The important thing to take from that is that there's no one-size-fits-all when it comes to parenting. You need to adapt and learn based on the children in front of you, because what works with one set of children may not work with another.