Here are my thoughts Harry. I voted to leave the EU with the, flawed, understanding that we would remain in the single market and customs union. It was madness to leave those economic unions.
I voted to leave because I didn't like the way the EU was heading, looking towards closer and closer political ties and before and since the referendum the EU has touted, and wants an armed force. I was dead against this.
Once Johnson became leader of the conservative party, my initial reaction was "oh ****" and it has remained the case. I regret my vote. Not because I want to be a memberr of the EU, I don't, but because it allowed Johnson to snatch power and has resulted in the worst government in my lifetime. On the other hand, this too will pass.
I would say that us not being in the EU has had no impact on putin's decision to invade Ukraine nor does it have an impact on where he will go next.
One final thought, to echo mutleys post, Starmer cannot campaign on a rejoin agenda for the next election. Your manifesto promises have to be achievable in a single term. This clearly cannot happen. What he has said is he will look for closer ties to the EU, which is all he can promise.