You are right. The modern generation (and I'm not sure which generation I fit into - being somewhere in between in age) have been sold this idea, by the people who make the money out of it, that everything must be made over, and up to date, or life is not worth living. My parents got married, bought a house, bought their furniture (from G plan) and expected to keep it for the rest of their days. And they did. And it was good quality and lasted them.
By contrast nowadays, people buy cheap furniture from Ikea or the like, and expect to change it every five years or so, to keep up with the current trends. Go to any recycling centre and the landfill skip will be filled with woodchip and plastic furniture, and the people who put it there will be tripping off to Ikea on their day off to get something else (made from particleboard and laminate).
Gardening is much the same - subject to the traditions of the day. It amuses me to see the gardens of the seventies, with their neat rows and circles of french marigolds and bright red salvia, with several inches of soil showing in between. My mother, in the 80s and 90s, tried to convince my father that it would be a good idea to plant things next to one another rather than at waving distance. Her theory was that he didn't want to spend the money on more plants! But he struggled to do what she wanted.
Children do try to bring their parents up to date. I did it to my parents. My mother's lounge being a case in point (I say hers, because my father had no design preferences). She had never been happy with it, and when I came home to stay in 1994, we overhauled it together. Their house was a design nightmare. The small kitchen had four doorways leading out of it, and a series of alcoves, necessitated by an old chimney breast and some ducts. There were tiled steps down to a damp lean-to scullery, and more down into a cold larder. There was no real room for cupboards or work surface. But they didn't seem interested in doing anything about it. Instead they spent their money on Caribbean cruises, and wintering abroad (presumably to get away from the kitchen!!)
A few weeks ago, our son told his father that his clothes were a disgrace, and he was going to give him a makeover. So he chose him some clothes which we brought home (OH just wears whatever he is told to - very obliging). I couldn't stop laughing - suddenly I was married to the oldest teenager in town. Skinny jeans , hoodie, etc.
I don't think young people understand that when you get older, you don't want to be chasing fashion, and whatever suits you, is what you will stick with, thank you very much. Sure, you might see some new trend and think 'that would suit me', but we are all free to pick and choose. Our middle aged friends don't laugh at us and tease us for being out of date. We are more secure in our tastes than teenagers. And as you say, their children have the last laugh, because it never occurs to them to overhaul the grandparental home - they love it in all its quirkiness. And they will be the people who start overhauling your daugher in time to come, and you can watch and smile