I'm surprised nobody has pointed out yet that "Mailers are another way to render a view" has lost information that was present in "Mailers are really just another way to render a view.".
The author of this post appears to want to adopt the most infuriating traits of the MSDN documentation: namely, converting all documentation into a list of facts ("Mailers are another way to render a view", "a common use of mailers is…"). This is bad because if you are presented with a bare list of facts, you can't judge their relative importance, or how they relate to each other. The original Rails example was bad, but rather than fix it, they have rewritten it to make the badness more obvious.
The original was bad not because it uses the words "just" and "simply", but because it's verbose while still being hard to read. I still don't understand what the sentence starting "Due to this" is trying to say, and it's very unclear where they transition from giving general technical facts to walking through the specifics of the example. (It is certainly wrong to call something "painfully simple" - I can imagine maybe one or two places where it's ever appropriate - but it's not the main thing that is wrong with those docs.)
But the first two sentences of the original docs were easier to understand than the rewritten version. Compare:
> Mailers are really just another way to render a view. Instead of rendering a view and sending it over the HTTP protocol, they are just sending it out through the email protocols instead.
> Mailers are another way to render a view. Instead of rendering a view and sending it over the HTTP protocol, they send it out through email protocols instead.
I mean, is it rendering a view or isn't it?! The second version explicitly contradicts itself much more baldly than the first version, where the words "just" performed an important function by indicating that the sentence is about what is different between mailers and other renderers.
In the rewritten version, two of the three sentences of the first paragraph explicitly contradict each other, and the third is totally unrelated to what came before. This was a structural deficiency of the original docs, but removing the narrative elements of the text has amplified the problem to the point of absurdity.