Hang on a minute, we were in the EU for over 40 years, meaning, rightly or wrongly, over 40 years of EU law taken into UK law. When we finally left the EU we could have removed all EU law from UK law but that would have meant a huge "black-hole" of no law over many areas of UK life. Regardless of what anyone thinks about it and regardless of whether or not anyone in the UK likes it, it is not humanly possible to replace over 40 years of EU law making in the UK, overnight, solely with home-grown, pure, UK law.
If the EU took over 40 years to produce a vast array of law that was incorporated into UK law then it may be reasonable to assume that it may take another 40 years to produce "pure UK law" to replace it. Judging by the way that some of our politicians pontificate, argue, debate, analyse and argue again it may be reasonable to assume that the time frame could be considerable longer than 40 years.