For one thing - you will be getting the curated highlights of their lives. You KNOW this. No-one posts on the nursery group/FB feed all the time they spend wrestling their toddler into clothes or vegging in front of the telly. I know I don't. Based on what I share you'd think all we ever did was gardening, rock painting and crafts. And you'd think they went a lot smoother than they actually did :P
Second: it doesn't matter what they do. What can you do? If you're not happy with your lifestyle only you can change it. You can do this either by reframing your own way of looking at it (compare down, not up; count your blessings etc) or by proactively trying to change it (side hustle, reduce outgoings somehow so can save more/pay off mortgage quicker etc). People say on here comparison is the thief of joy, but that's only true if you spend your time looking at what others have that you don't instead of focussing in your own resources.
Third: This is political and if you want to harness your (perfectly natural!) jealousy into something productive, then become a socialist, vote that way and encourage those in your sphere of influence to do the same. It's NOT fair or necessary little Jago has so much better a standard of living or opportunities than your child, any more than it's fair your child gets to have a secure roof over their head and homeless children living in temporary B&B accommodation or DV Shelters do not. The issue is capitalism and consumerism and neoliberal politics. You can either manage within that or fight to change it.
Personally lockdown has made me realise I have plenty and need much less, even though I am far from the richest. I am trying so hard to remember to focus on what really brings me joy (and it's never the expensive things) and not to worry about the rest. But then I never expected to have the kind of life I do now, it seems ridiculously comfortable and grown up to have a child, a mortgage, a job, some actual savings. I'm a much more 'hand to mouth, low commitment, limited planning' person by nature.
My partner was always very ambitious (almost entitled in some ways, he went to a posh school and knew families a lot wealthier than his own so I think that set his expectation levels for his future high) and struggles a lot with the 'grass is greener' way of looking at the world. I always try and remind him he's looking up at an elite from a very privileged position himself, but it doesn't help him and I suppose it might not help you. So instead I try to support him in the plans and projects he has to improve our situation as he sees it; but I'll have no truck with being told we are bad off or don't have enough. It's just not how I see it.