Since everyone can use a tracker of sites, that allow it, it does not create an unfair situation. Its just the same as training sites or solvers or whatever. Those who spend time and money on poker training and software have a higher chance of winning than those, who dont. So its up to each player to decide, what kind of investments they want to make depending on the stakes, they play, and why they play.
Just another tool. If the site allows it during live play I'll use it and if it doesn't I won't. I can with it or without it. So pretty simple.
With that said I don't completely depend on the HUD as that would be stupid cause even as I've played 20+ years now....I still run into plenty of players I've seen before, ones I have very few hands or not enough to draw strong conclusions on. What such software is actually great at/for is using it for studying. Easiest and best way to study and do hand reviews. That's where such software really excels for me.