A very common overlooked cause of your symptom is an overtightened gearbox or a frozen ball joint. It has to be quite out of alignment to get such a symptom otherwise. Really wore out cars can be made to track well if aligned and nothing is binding.
The problem with the overtightened gear box is that the tech is looking for something different altogether. At the wheel its hard to feel an overtightened box. The ability to overtighten is the reason MB says the adjustment has to be made on the bench (and is the reason I never take out the last bit of play while correcting on the car. The way they drive overtightened is the worse driving experience the front end can deliver.
Bosch Master, ASE Master, L1
33 years MB technician