I think a level of formality and respect is a good thing and I would never have appoved of my children calling adults by their first names unless the adults invited it, which, largely they did amongst friends. Older men and wmen were always Mr and Mrs So and So.
I strongly deprecate the generation older than us being 'first named' by public sector workers. When my MIL was called by her first name by health and care workers uninvited I thought it hugely disrespectful.
My BIL called his parents by their first names and I thought it a symptom of something very odd in their family. My sister has caught the habit and after years of being 'mum' to her, my mother is now being called by her first name which is belittling and rude - and is clearly intended to be.
I see that some people who have posted above have airily dismissed the conventions. I would respectfully suggest that they can do this in their own case but in the case of others, particularly the old and vulnerable, to dismiss formal respect towards them is also to invite and encourage disrespect and ill treatment. Those who are given an inch often take a mile.
As for youngsters deserving more respect than adults I suggest this inversion of the natural order invites 'spoilt brat syndrome'. Babies, children and teenagers deserve protection,sustenance, education and kindness but they have not yet put anything into the human equation to deserve more respect than the adults who are giving them everything they have.That the ego of the young has been stoked by liberal upbringing is evidenced by the self-centred, narcisstic behaviour of the present snowflake generation who have grwn up with a sense of entitlement without having done a thing yet to deserve it.
I always encouraged my children to be polite and respectful to 'grown ups':- teachers, parents of frirnds, employers and so on and they are now both employed and well liked. Many adults have commented on how 'nice' they are as if this was a quality dropped from heaven when in fact it was sound early training and our instilling a respect for humanity outside themselves.
Because, in the end, that is what respect is, a recognition that we are not the centre of the universe and that others outside ourselves are human and deserve as much consideration as we pay ourselves.