I'm a Millennial. For me, it isn't so much that I begrudge earlier generations for having it easier (and several other people are correct when they say that earlier generations had their own problems too), it's the fact that it is fashionable in the media to blame Millennials for not being able to afford their own house, be in a worse position than their parents etc. If earlier generations would admit that most people born post 1980s simply won't be able to afford things that they could because of rising prices and lack of job stability, I wouldn't mind. But instead, we're simply portrayed as selfish, childish and lazy. That attitude (which doesn't come from all previous generations, I agree) is what really upsets and angers me.
We can't afford a mortgage and children because rising house prices, lack of employment, low wages and the fact that jobs for life aren't really a thing any more. Not because of avocados and smartphones!
Speaking of smartphones, when they first were introduced, nobody needed them. Then, for better or worse, society changed so they became necessary. Look at how many apps we had to download to get out of lockdown. We couldn't enter a building without scanning a code, and you can't scan a code without a smartphone. That's just one example of course, but it is indicative of how society changes to create a demand: that is, the demand fir consumers to buy smartphones and make money for the tech industry.
As for me, my smartphone was a freebie to say thank you to my DH for staying with his mobile company since 2001. I got it in 2017 and I'll be keeping it until it dies. I can't afford to replace it, so I'll probably have to go back to a "dumb phone." Though I can't say I'd mind all that much.