That graph is misleading due to only 30dB total spread on the y-axis and then on the X-axis it's showing up to 60kHz for some unknown reason, and it's above 20kHz that the frequency response gets real funky - so if you put it all into perspective you see that the response is "only" varying about +/- 4dB from 60Hz - 20kHz. So it's not good, but it's nowhere near as bad as it looks in the graph you linked.
A lot of speakers use a very similar response, a dip in the 2-3khz range, and a bit of boost in the 8-10 khz range.
I have read that many like that sound, it keeps vocals and similar sounds from being "Too" forward and allows clarity at the upper end for listeners that have older hearing.
Not saying it is ideal, but I have owned speakers that were flat in the mids and also this type.
The "Dip" ones sound a bit recessed, but are more listenable long term for sure.
The ones without that "Dip" came across as the singer was right "There", but got tiring at higher levels.
The highs, listener dependent.