At first i did not want to upload this photo at all as I don't really like it but then I thought about highlighting what is wrong and how it could be improved.

Please keep in mind that I am new to astrophotography! However I think that this makes it possible for me to make mistakes, highlight them and then (hopefully) also tell how to fix/avoid these. I think most pictures shared here on astrobin are really pleasing and well done. However that is sometimes not very helpful for beginners.

1. I did not take any calibration frames
Yes today's processing software has become really smart. However it did not (and to my knowledge can not automatically) fix dust on the sensor or optics. You can easily spot right in the center a dark spot (bottom right is another one) - thats dust. With light frames it would have been automatically removed. Since this picture I always took calibration frames.
Solution: Always take calibration frames! (Also check if you already have dust on the sensor or in the optics and clean it)

2. Newton telescopes have diffraction spikes. They look odd when they are not 90° or 45° aligned.
Framing is important, the center does not need to be always dead-center. But rotation also is on newton telescopes.
Solution: The rotation between the telescope and the camera needs to be in 45 or 90 degree steps.

3. Primary mirror clips can create diffraction artefacts around bright stars
You can see (especially on the two bright stars on the left) that the "shine" is very uneven. This is caused by the clips which hold the primary mirror (sometimes even the focuser can create this). I now use a "Mirror Mask" or "Aperture mask" which makes it perfectly even. You can 3D print, buy or even make them "by hand". There are a lot of posts and videos around this topic. I am not sure if this happens to all newtonians, this picture was taken with the Skywatcher 200/1000 PDS.
Solution: Add an aperture mask

4. Coma
There are a lot of posts and videos around this topic, I will only describe it with one sentence: "all stars not in the center look like comets". They should be round and a coma corrector does that. Solution: Either crop to the center or get a coma corrector (I now have the Baader MPC Mark III and it solved it for me).

5. The Pleiades do not fit very good into my field of view
My rig has 1000mm focal length and an APS-C sized sensor, that results in roughly 1.3 x 0.8° FOV. Target and FOV needs to match. In my opinion that picture is "okay-ish" but with a wieder FOV it would look way better.
Solution: Pick targets which fit your field of view (or use different equipment to make your FOV fitting)

6. Not enough integration times / light frames
To be fair, this is what everyone will say about nearly every picture. However the reasons may differ. In this case I will tell the reasons and how to overcome them:
At this point of time I only had a Mount, DSLR and telescope. I had to take the pictures manually. Sitting outside in the cold and pressing the shutter button every 30 seconds is boring and annoying. After 120 shots I quit.
Solution: Automate it:
- use an intervalometer
- (Canon DSLRs only): use the custom firmware "Magic Lantern" which includes an intervalometer
- use a Notebook with software to take the shots automatically
- use AsiAir or Astroberry

I am really sure that there are more things which can be improved on this picture, feel free to mention them if you think that this might be helpful for others!