You should read this blog post from Nielsen Norman Group about the way that flat design can cause problems (for that read frustration) for older people.
His summary says: UI elements with absent or weak visual signifiers condition users over time to click and hover uncertainly across pages—reducing efficiency and increasing reliance on contextual cues and immediate click feedback..... Some designers argue that it’s ok if older users don’t find flat design intuitive, because flat interfaces are targeted at younger users, who ‘get it’. '
You probably think, surely no designers could be so daft. Dream on.
What Nielsen's research found was that those aged 18–30 do seem to be better than older adults at detecting clickable elements, even when they have absent or have weak signifiers. There are lots of explanations for this but my guess is that it the obvious is true (i.e. the young spend more time hovering around on web sites and apps).
BUT, if any designers are reading this blog this finding is for you - 'Despite their ability to navigate through clickable elements with absent or weak signifiers, young adult users don’t enjoy click uncertainty any more than other user groups.'
I loved this quote from one of the young testers “I don’t [know what’s a link]. I just start clicking and praying that it works.”
If something is an active link then give me (an oldie) sufficient visual clues rather than making me guess. It will even help my Goddaughter. Dick Stroud