You're still missing the point, jourdain. The UK may of course amend its laws on leaving the EU (although I think it still had that right before, so...) -- but the Repeal Bill appears to imply that it's Ministers rather than Parliament who will have that right -- albeit with certain restrictions, and for a limited period of two years after "exit day" (and maybe a few months before then). That may flirt with the idea of parliamentary sovereignty. Not in the same way that Article 50 notification was deemed to have, because if passed in its current form this would be Parliament giving permission to Ministers to exercise such power. But that still leaves the question as to whether they should have such powers. Perhaps there's some cold logic to it, because there's a lot of legislation that may need some modification or other, and it might take a lot of time to sort through if Parliament were to be fully involved in each and every such change.
That's where the debate is. The principle that EU law should be implemented into UK law on withdrawal was never, ever, ever in question. Only the manner in which that's to be achieved.
As I say, I'm not sure I have the technical knowledge to understand myself what the Bill says, although I have been reading the text. Others who matter do have such concerns, though, and it's them you'd have to persuade to set aside such concerns, or to recognise them as mistaken, depending.