Parties don't win elections; they lose them. And Labour has consistently been losing elections since the New Labour years.
I think it is worth saying that Labour have only been in power for roughly a third of the last 100 years (about 34 years), and that includes the 10 years of Blair. They are, essentially, a party with a history of opposition.
I would argue the prime Labour years were the Attlee and Wilson years, and even then you are only looking at 14 years. Wilson's first six years as PM is equal to David Cameron's term, for heaven's sake.
For the British people to return a Labour government, there needs to a certain set of circumstances.
First, there needs to be some sort of sensible public expenditure commitment: Blair did this by committing to Tory spending plans for his first term of office.
Second, the country needs to feel the Labour leader is on their side and will improve things that affect their day-to-day lives: Blair did this with "Tough on Crime; Tough on Causes of Crime " and "Schools and Hospitals".
Third, the country needs to be in a place where it feels safe to take a measured risk. In '97, the Tories weren't crap or useless, per se; they were boring. Blair had a bit of vavavoom about him; he exuded the notion that "things could only get better." And that struck a chord with people.
What do we have now with Labour?
We have a public spending attitude that seems ill-considered at a time when there is post-lockdown pressure on tax receipts and huge public spending on lock-down measures. We have a strange obsession with culture wars, to the point of elected Labour MPs not being able to attend conference due to stating material facts. We have an at-the-time deputy leader calling the opposing party "scum". And we have a Labour activist presence that seems to relish being vindictive towards the general public.
No wonder long standing party members are leaving in droves, and the electorate aren't voting for them.
Boris is a total disaster (and the Tories know it, hence the knives coming out), but Labour is in no place whatsoever to capitalise on anything.