Well, ikky, if that had been the case, if you think the UK economy is in a bad way now, it is in tip top condition compared to how it would have been had we adopted the euro.
Why do you say you wish we had adopted the euro? Imposition of the Single Currency was arguably the single biggest blunder (among many candidates) that the Euromaniacs contrived. It has been an absolute disaster for many of the eurozone nations. There is one definite winner and another (France) who thought it would save them from a German dominated EU but it didn't. A very few others who have just about held their heads above water since its launch. The rest have struggled since its inception and a few (Greece, Italy and Spain for sure) have seen their economies shredded since adopting it. It's true that the economies of those countries were problematic to say the least, but having no control over their exchange rates and interest rates has left them absolutely shattered. The UK, also stronger, would have been in the same position, especially when dealing with the 2008 financial crash and the crisis of the euro itself in 2012-13.
It is widely acknowledged by just about everybody except the Euromaniacs that the introduction of the Single Currency was a monumental mistake. However, it will not be reversed any time soon because those able to make that happen will not accept that it was a blunder. Like they have with trade, they see the Single Currency as an ideal way to force together nations which otherwise might diverge onto different paths. They were wrong with trade and they are monumentally wrong with the euro. The trouble, as the UK found with Brexit, is that the strategy of disabling national legislation and replacing it with the European version makes it extremely messy to reverse the process and it is a mess that most users of the Single Currency simply cannot afford.