There is a lot of truth in what you have said, but what I would take issue with is that Corbyn's policies would have ended up like Johnson's or in fact be anything like how he handled things. The two were as different as chalk and cheese.
Corbyn's weakest area was Brexit, but I don't see he was driven by the referendum result - Johnson seized an opportunity for power by changing from remain to leave, what his public pronouncements, he was never an advocate of leave in fact I struggle to think of a policy or principle he has got (apart from feeding his own ego and making money as easy as possible.).
Whereas whatever you may think of them Corbyn does have strong ideas and principles and had a range of policies - I mean who would have thought nationalising the utilities would be a good idea?).
In terms of Brexit, Corbyn was in a bit of a bind, he personally distrusted the EU- indeed many unions did ironically seeing it as an attack on workers, whereas the right saw it an attack on capital doing as it wished! However, his proposal, which was to negotiate a deal and then put that to a ballot - that was overlooked by a welter of other policies. One of the issues was Corbyn wasn't fixated on Brexit to the degree Johnson was and who made "Getting Brexit Done" his slogan, a classic right wing political trick - a simple slogan with absolutely no substance behind it.
Corbyn was not slick enough and could not get his ideas across ( a real weakness, but an ironic one, seeing as people claim to want truth, straight talking and real ideas as against slick smart suited politicians making vague promises, but always seem to vote for the latter!). The lesson there is that the average voter likes a simple proposition, not a realistic set of policies.
I suspect that we'd have end in a softer Brexit and with better relations with the EU, not had the noisy, childish arrogant stance taken by Johnson. But we will never know, there clearly was a better way of managing Brexit, but I guess when you have promised something that could not and can never be delivered, then one has to make a lot of noise and find scapegoats to hide the reality.
As for Covid, interesting really, again yes there may have been the same advisors, but the way it was handled would have been very different- Corbyn certainly wouldn't taken the "its nothing but bad flu" approach combined with a "herd immunity" policy which Johnson tried in the early days.
We certainly wouldn't have seen the billions spent on PPE, and testing etc. that somehow was all directed at firms operated by people many of whom were relatives, or donors or mates of Tory politicians. So £40 billion plus would have been saved there for a start!!
I really don't get this anti Semitism stuff! Well I do, its a deliberate smear campaign because Corbyn was notably in support of the Palestinian cause - it was used, disgracefully in my opinion by centre right Labour party members and certain members of the Jewish community to smear him. he certainly did not advance any anti Semitic policies or causes.
Were there internal party issues? yes, that is definitely the case and they weren't handled very well by the party and the matter wasn't dealt with well by Corbyn. But was that worse or any different from similar issues within the Conservative party? Having looked at this I can't see any evidence that this is the case. Being critical of Israel is not anti Semitism.
Why tot he average voter the internal machinations of a political party would matter is puzzling, surely what they do in government is whats important?
Its tempting to say that the Ukraine war is solely the cause of current issues. But IF we had a decent Brexit deal then the impact would not have been so great and lets not forget, that a decade or more of poor economic policy and reckless quantitive easing has fuelled inflation. Corbyn i suspect would have reacted very differently to Johnson and we would not have this insane focus on tax cuts.