> "How about deciding what you want to say: a) scrum makes it worse or b) scrum does not help?"
Both!
> "Really? Before we have worked with RUP and Agile RUP. Compared to that Scrum is tiny."
Nuclear submarines are tiny because aircraft carriers are large. And this means submarines are a good investment.
> "The team should be cross-functional based on the product the team develops."
This is ignoring reality in many cases. A team might develop something domain-specific, like a natural language processing algorithm, but then later the product requires a web service and a front-end. As a result, management requires specialist machine learning researchers to spend their time writing front-end widgets, because "Scrum says to be cross-functional" (and don't even think of saying the no-true-Scotsman reply, "but that means they're doing Scrum wrong!" Scrum leads them to that type of thinking).
In many cases, the different functionalities for a single product should absolutely not be embedded in the same team. Rather, much like in software design, it's important to separate concerns, and have teams with modular and clearly defined boundaries between their different and complementary skills. Then for a single product, parts of it will be worked on by different teams that each have specialized skill in one area, and can operate independently of each other because it's not muddied by an artificial requirement for "cross-functional" skills.
Some other times, Scrum-like cross-functionality is good. That's why Scrum is wrong to unilaterally prescribe it for every product and every situation. Sometimes it's good, sometimes it's bad, and teams need to be empowered to customize according to whatever the case at hand needs, not the unilateral model that Scrum tries to impose.
> "This actually presumes that I identify successful practices which can be applied in many projects. We did."
But then what do you say to people who have identified successful practices over decades that conflict with Scrum and are mutually exclusive with Scrum's approach. Scrum worked for you. Great. It didn't work for me.
What's your reaction to that fact? If your reaction is to say, "well then you did Scrum wrong, because it always works" then you are just denying the premise that any other solution could be possible, and it absolutely is a No True Scotsman fallacy.
Can you at least admit that some people have earnestly tried Scrum in a situation when Scrum is advertised to work, like iterative software development, and they did not "do it wrong" yet still found that it didn't work for their team?