Evolutionary Tree

[Esquilax]

The fact that the phylogenetic tree is not as predicted and has problems matching the data to the theory means there is still much to learn and still much to prove to get 'common ancestry' to the point where we know how it works.

Learn your philosophy of science: science is a probabilistic field, it accepts and rejects explanations for the available evidence based on probabilities, not sure fire truths. There are holes in every theory, but the fact that we can't explain gravity- and in fact, a lot of our science is demonstrably wrong regarding that particular force- does not grant you license to slyly assert that maybe gravity doesn't exist, and angels hold us all down to earth.

If we don't know how it works how can you call it a fact?

The same is true of gravity. The problem here is that you're committing the "99% = 0%" fallacy: just because we don't know everything about something does not mean that all of our observations don't pan it out anyway.

If common ancestry is not a fact and still only a theory,

Learn your basic scientific terminology: theories are not "only" theories and not facts, theories are explanatory frameworks made up of multiple facts working in concert. Does it... trouble you at all, that you don't understand even how extremely elementary scientific terms are defined?

then the big picture of evolution (defined as end-to-end explanation of the diversity of life, common ancestry, decent with modifications) is also not a fact, but only a theory. Is that a fair assessment?

Yes, because theories are comprised of constellations of facts. They are, in reality, much much stronger than a fact could ever be.

It's your conclusion that isn't a fair assessment.