Is there a reason to be worried about go-arounds as a passenger?
A go-around is nothing to be worried about as a passenger.  What would be worrying is if the pilots elected not to go around when conditions warranted it.  

The dark likely isn't an issue with this go around as approach lighting systems can become exceptionally bright when requested (to the point you'll need sunglasses to look at them if visibility is good).  What was likely a factor was fog.  Airplanes need a minimum amount of visibility to land and if conditions are marginal you won't really know until you fly the approach and either see the lights and land or do not see the lights and go around.  For normal ILS approaches you would initiate this go around at 200 ft above the airport elevation.  For very low visibility approaches this decision height may be 100 feet or less above the airport elevation.  

The point at which you go around if you fail to see the runway environment is well defined and procedures ensure obstacle clearance so there is no danger as long as procedures are flown as published.  

Another possibility for the go around could be the airplane in front of you failed to clear the runway speedily due to low visibility.  If the preceding aircraft was still occupying the runway then your airplane would have to go around.  There are a few other issues that could warrant missed approaches (e.g. windshear) but in all of these cases the go around is the safer option than proceeding with the landing.  

Your pilots made the safe decision to go around and this is what you should take from the experience.  There is zero reason to be worried.



To address your added specific questions:


Flightradar24 flight track data is unreliable.  It is neither true radar positioning or necessarily true GPS positioning.  It is nice for zoomed out flight tracks but is not reliably suitable for the precision during landing/takeoff.  Do not use it as a basis for worrying that your approach was not properly aligned.
Extremely rarely if you mean not being aligned with the runway.  Uncommon if you just mean not seeing the approach lights but otherwise on course to land.  The navigation signals used in ILS approaches are broadcast down the runway centerline for the lateral guidance and from just next to the runway approximately 1000 feet past the beginning of the runway aimed 3 degrees up for the vertical guidance.  These signals are only usable in a cone that radiated outward from the runway.  Furthermore the navigation accuracy of the ILS receivers are regularly tested on the airplane.  Combined with monitoring by air traffic controllers you will not end up on a parallel course that does not intersect the runway.
The vertical data is also not reliable.  Your airplane approached on the glideslope and if it made it down to 50 feet this would have been just over the very beginning of the runway.  After initiating the go around it would climb (likely to between 2000 and 3000 feet) and attempt another ILS approach.  At no time is the airplane lingering at 50 feet above the ground anywhere but over the runway for a very short period of time.  




The video below is an example of a very low visibility approach and you can see an example of how low the airplane can get before visual contact is made with the approach lights and runway.  At predetermined points based on the aircraft, airport and crew qualifications the airplane would initiate a go around if these things were not seen.  For standard ILS approaches this would be when the airplane announces "200 feet".  For category II ILS approaches, it would be at "100 feet".  In the video below a category III approach is shown which has an even lower altitude to initiate a missed approach.