Engines in full reverse, I see.
The real question is does the analysis of pre-brexit and post-brexit growth take account of non-brexit problems? Using Germany as an example, it is clear that the claimed 6-8% Brexit reduction effect is nothing more than a simple analysis of the trend line. i.e. it was going like this, now its going like that.
Meanwhile the UK has moved up in global rankings
Europe's biggest economies have slowed sharply compared with their pre-2016 trends, and each has its own distinct drag — Germany's energy shock and industrial exposure, France's fiscal and pension strains, the UK's investment weakness and trade friction with the EU. That shared slowdown is a big part of why economists disagree on how much of Britain's specific underperformance is attributable to Brexit versus common European or global headwinds.