How dangerous was this approach of a Dash8 Q400 really?
The relevant TAF that the pilot would have seen before going there is below (only showing the bits for the time of landing):


  TAF AMD EDDL 180929Z 1809/1912 22025G40KT 9999 SCT035
  TEMPO 1809/1813 26035G50KT
  PROB30 TEMPO 1809/1813 26045G65KT SHRAGS BKN015CB


So the pilot was aware of a strong cross wind possiblity, but even 26065KT is 27 kt crosswind (runway is 233) which is within the limits of the plane. So there was no reason to divert before getting there.

The metars just before and after the landing are below:


  METAR EDDL 181050Z 27045KT 9999 SCT037 BKN043 08/00 Q0993 TEMPO 27045G55KT=
  METAR EDDL 181120Z 27034G48KT 9999 -RA SCT028 BKN038 07/01 Q0995 TEMPO 27045G55KT=


So the "baseline" was 27045KT, i.e. 27KT crosswind, and the maximum gust wind was 27055KT, or 33kts crosswind, just 1 kt above the plane limit.

Note that the metar wind indications are rounded to the closest 10 degrees, so the worst case could have been a wind from 274 degrees gusting at 55 kts, or 36 kts crosswind.

We can assume that the pilot decided to continue the approach based on the wind information provided by the tower.

Whether the pilot should have aborted at the last second because the landing was not going as planned is hard to gauge on a video, but based on the information we have, the wind parameters were ok.