Exactly. There's absolutely no reason to think that advanced life did not exist on Mars except for the lack of evidence. That sounds funny, but the absence of evidence is not evidence of absence, especially in a case like this where the planet has been probably sterilized on a time frame of potentially billions of years.
The Great Pyramid of Giza is a massive and extremely hardy structure that will outlast all modern buildings. Yet it's substantially deteriorating after less than 5,000 years, and it will eventually just completely disintegrate, absent the already ongoing preservation/restoration efforts. It might take 20,000 years, maybe a million. A quick search on the internet suggests nobody really knows, other than that it will happen. And now we're talking about time frames of billions of years. So what would a sterilized, perpetually radiated, atmosphere free Earth over billions of years look like, paired with never-ending massive dust storms (as on Mars)? Well, probably not especially unlike Mars does today. But oh what treasures would await you far below the surface!
I don't necessarily think anything does await us, but who knows? It's a tantalizing possibility that we won't be able to dismiss until we have humans on Mars. It's vaguely analogous to the early observations of 'canals' on Mars [1] whose explanation ranged from running water to active geoengineering from another advanced species on the planet. Their exact meaning was debated all the way into the mid 20th century, until we finally were able to get probes that could take 'high res' photos of the surface that showed they were definitely just optical illusions. A disappointing discovery, but nonetheless emphasizing that the importance of actually testing things instead of just relying on indirect instrumentation/data of this era or that.
[1] - https://en.wikipedia.org/wiki/Martian_canals