What I wonder, now, is rather what the point of shooting film is when people have to edit the negatives in hindsight. Am I wrong in thinking that by having to make a positive out of the raw image of a negative, by having to apply contrast and changes to highlights etc, the original characteristics of the film I chose are being distorted?
I think you have a few misconceptions about film. Color reversal film, aka slide film, can be displayed by projecting its image. This is essentially displaying the truest form of the captured image per the film.
Black and white and color negative, on the other hand, need to be turned from negative to positive via printing. I've less experience with printing color negs, but a solid amount of black and white, so I'm going to focus there.
When printing, you can dodge and burn to decrease/increase local area exposure. You can swap contrast filters to adjust the contrast of the image as a while or use with dodge/burn techniques to adjust contrast in local areas. You can stack negatives. In fact, most of what you'd call "photoshopping" is a toolset inspired by darkroom techniques.
Let's also not forget that printing paper has a shorter range or latitude than film, and film less than the world. So, you've compressed the world into the film and compressed the film into the paper - creating a representation of the world that lacks in both the total range of brightness and detail of the world.
Understanding that, we choose film and developing processes that will support the ability to gain the envisioned print. The negative isn't the endgame - the print is - and the negative is simply a step to getting there.
The characteristics you talk about boil down to grain structure and the ability of that film to represent the scene such that you can create the print. Changes to contrast, highlights, shadows, exposure, etc. are all par for the course. This isn't changing the character of your film - this is exploiting it for its ultimate purpose.
Whether you do this in a dark room or via scanning and on a computer is neither here nor there. Point is, your 135 FP4/Ilfosol, no matter the processing, will never look like my 120 Delta3200/Rodinal. Even with all that processing, the film and development still matters - it leaves its mark on the image because it was the image, for a time.
What is a professional way of turning developed negatives into digital files to keep the original characteristics of the film?
Simple: Scan them. Learn to scan such that you get the best range from your negative. Make sure that your highlights are not blown nor shadows too dark. That's the best you can do for that step.