Mainly: my co-workers who have been at the company longer than I weren't very helpful with onboarding me! We're a little company, so documentation of a bunch of our software is non-existent and the specialized hardware setup we have has a lot of quirks I had to slowly teach myself the last year. I'd hit lots of problems that'd take 5 seconds of their time to diagnose and fix and I'd end up stuck for over an hour while waiting for them to answer a Slack message - or they'd randomly drop offline.
So there I am, working in my bedroom in a new job wondering if I'm a needy little snowflake not digging hard enough or whether the people I work with are just unhelpful because... reasons (still haven't met them in-person since my pre-pandemic interview). After a year I think it really is the latter, but it made me grumpy my early months here.
That could be a possible source of resentment from newer, younger employees. Set us up for success!
I still prefer working from home, but I did commute to the office for a happy hour recently. It was nice to randomly get coffee with the CTO in the morning and hang out with new friends in the evening - none of the "unhelpful" people showed up! :P