4.5% includes everyone with some level of colourblindness, but total colourblindness is much, much smaller (at least by a couple of orders of magnitude). In terms of demographics, women are much less strongly impacted (around 0.5%), and Caucasian men the highest with almost 10%.

Addressing an issue that affects 10% of a particular demographic (especially when that demographic is over represented on the internet in general) is wise, but the answer is not just “choose better colours” because of the many different forms of colourblindness.

The answer is choosing sensible defaults (stick to frequently used patterns your users have encountered before), support with high-contrast iconography and shape where possible, and don’t rely on colour alone for any part of your design (use tools like https://www.toptal.com/designers/colorfilter to see how your design survives through colourblind eyes).

By total colourblindness do you mean achromatopsia? It's like hearing someone says 42% of Americans have obesity and making a remark this may be true to some level of obesity, but TOTAL OBESITY is much much smaller, at least by a couple of orders of magnitude :D

Not quite. I'm talking about monochromacy, which includes achromatopsia, but casts a slightly wider net.

Anyway, my main point is that although I'm technically colour blind, unless you're using particularly muddy shades of red and green, or particularly small splashes of colour, it doesn't matter too much. The key goal is to avoid colour-dependent design, but not to be afraid of colour either.