Generational Design Expectations Inertia happens when people start to experience new trends in design and have their habits settled soon after.
For example
In the early 00s online banking was new. Difficult to work with and hard to get used to. But once the habits crystallised those people, when got older, formed a core base clientele of those companies dictating what they perceive as a good user experience — mostly confusing it with their long formed habits. So “good design” for them is totally different to what it is to the following group of people whose expectations have being formed by other more modern companies.
Most attempts to update the designs of those companies (legacy banking, amazon, giant long established brand with online commerce etc) was either a none starter (banking) or led to a massive daily turnover drop which promptly meant the the design had to be reversed back.
Different companies deal with it differently. Banking mostly just created a different set of brands and apps to cater for the expectations of their younger generations. Amazon lags behind trying to thread a needle slowly updating its designs keeping it the same for various groups, long established brands with online commerce elements tend to leave their checkouts (most sensitive areas effecting turnover) to be updated last, slowly and bit by bit, a/b testing every little thing before proceeding.
So what is a good design?
The one that follows the latest trends everyone is doing or the one that increases turnover by 20k per day? — Sometimes it is both. Everyone deserves good design I believe. But what Generational Design Expectations Inertia means — is that good design is not the same for all generations — especially if you want to optimise for the turnover based on your core clientele that is.