At the end of the day though, the debate is futile. We had a referendum, the majority of those who voted put an x in the box to leave, so we left. That's how democracy works.
This was posted by a remain supporter who has lost their job due to Brexit, but they understand how democracy works. The same poster also acknowledged that the opportunity to cancel Brexit was presented in the 2019 GE, but remain supporters did not capitalise.
To be fair, the OP only asked for one benefit, and didn't specify who it should be a benefit for
Nor did the OP specify for how many people the one benefit should apply.
A Brexit benefit for me is that since the UK fully left the EU in January 2021, UK Citizens must follow the 90/180 Schengen guidelines for time in the Schengen zone. This, coupled to COVID demonstrated how much work can be done from home, created hybrid working.
Since January 2020, I have worked in the EU more than anywhere else. The attraction for EU companies to employ non-EU is that it allows local staff to work hybrid too on the basis of equal fairness. The French energy company I work for now has more non-EU persons than EU in both the London and Paris offices.
Companies have been able to save money on office costs too due to hybrid working.