Other than, ..” ...I guess soft tissue can survive...millions of years....”
The possibility that fossils could be younger cannot be allowed. yet fossilization (mineralization) does not take long at all (decades) (longer for more complete).
Reminds me of the punchline "frog with no legs can't hear".
You can allow that is a possibility to your friend. The wonderful thing about science is that you can follow the evidence, and you can design and construct experiments that prove or disprove a theory.
You can simply insist that both of those possibilities are likely, but if you were assigning PROBABILITIES, which would have a higher probability?
Fact is that this is one more evidentiary element.
I had a thought the other day that it should be a law of ethical conduct within the scientific community that if one was stating a theory, or postulating some sort of guess, that you should be required to say something along the lines of, “It is our belief, based on the best evidence we have that . . . “
This is how global warming became a fact. It was a lie repeated sufficiently that billions and billions of dollars and many careers have been wasted.
Science is in very bad shape at the moment. Stating something definitive about a theory or belief should be a career-ender.
Under some conditions, fossilization can be delayed for many thousands of years and longer.
For one famous example, consider mammoth carcases found in Siberia.
For another, Neanderthal bones with some intact DNA.
For another, consider insects preserved in amber -- which became the basis for the fictional story of Jurassic Park
Yes, those minute amounts of alleged dinosaur soft tissue seem now likely to be that, but is not yet definitely proved.
No DNA has been recovered, and so other possibilities still exist.
But if we assume these minute tissues are dino-remains, then they would first suggest that other conditions can also preserve small amounts of organic material much longer than previously expected.
So your basic assumption -- that organic material must always fossilize or quickly decompose -- is, well, unwarranted.