As I've got older, I need fonts that are larger than what the gurus at Apple seem to desire. On a 5K iMac with a 27" U2720Q (4K) right hand side monitor, I have

As I've got older, I need fonts that are larger than what the gurus at Apple seem to desire. On a 5K iMac with a 27" U2720Q (4K) right hand side monitor, I have most web pages at 110%. What I don't understand is why we've somehow got to the situation that a measure of font size has become resolution dependent. I'm just physically measure an "M" on my web browser, and it's 4mm (0.16" or 12pt). The Mac insists on using somewhere between 8pt and 11pt. I can't expand that by the minor variation without losing lots of screen space. I don't want a larger screen because the top of the screen is at eye level, which is the correct position ergonomically.