Afrika has a lot of landmass around the equator, while the others are at the edges where in the mercator anything is stretched out. Europe and north america appear bigger than they are.

That is factually correct, but what is the impact of it? Why does it matter concretely?

Does it matter whether things are true, even if their impact is not readily apparent?

Now, as to impact, one could argue distorting the relative sizes of landmasses causes geopolitical ignorance. For example: do people understand how relatively small western Europe is, the ramifications of that for their political unity, transport system, and impact on the world?

Showing the true size of Africa helps to put into context its challenges with regional transport, political unification, flow of ideas, etc. It also shows that Africa is actually has a relatively low population density. It also makes it easier to understand why lumping everything there under an "Africa" moniker is weird.

As a side effect, the sizes of other regions like South America are also shown more accurately.