When scientists argue then this is progress!!!
I understand this is difficult to understand for non-scientists, so let me try to explain. Whenever an interesting topic arises, scientists gather data, make quantitative analysis and compare this to a possible hypothesis. The terms theories, models are also used. When a model does not agree with the data it is discarded. Scientists then write up their study and submit it to a journal and/or arxiv where it will be peer reviewed. That means other scientists who are also specialists in the area read the paper very critically and pose difficult questions, i.e. scientists argue. Only if these are answered to their satisfaction the paper will be accepted by a legit journal. At the end of this scientific process wrong claims will be ruled out.
However, science can only falsify claims, e.g. the world is demonstrably not flat. When a hypothesis or model passes all tests, it becomes accepted as correct and we usually call it a theory, e.g. evolution can explain all life forms on Earth. Scientists still argue about details, e.g. before DNA sequencing, the hippotamus was seen as closely related to the pig, now it looks like the whale is its closest relative, but evolution is accepted as a fact.
For Covid we are still learning. Peer review of papers is often still ongoing, however as results are time critical, they are being discussed in the press and used by politics. This can be very dangerous, but with Covid we did not have the luxury to wait. In fact countries that acted fast did much better then the UK which wasted almost two weeks in March after Italy had reached 1000 deaths. However several Covid facts are agreed upon already, e.g. the fatality risks depends strongly on age and it makes it worse if you are diabetic.
Regarding the date of Covid entering humans, there are already over 10 studies which all give a range typically November to December 2019 with 6 Oct 2019 to 17 Jan 2020 as extreme values, see Table 1 of
https://www.sciencedirect.com/science/article/pii/S1567134820301829. To me this looks very much like an emerging consensus.
Unfortunately absolute truth does not exist in science. If you want unequivocal truth you need to turn to religion, but then it is not science. Science can be confusing and scientists can also make mistakes, this is why it needs peer review and important results need to be corroborated by other scientists. That said science is still the best way to make progress. In fact I would argue, it is the only way.