I think you'r right, Grantanow, sadly. I really do wish the stars would align to make it happen though. People seem to struggle with the fact that Starmer is not charismatic and Burnham has a media presence. There are obvious problems with factions within the LP, and Burnham does seem to inspire unity.
Also, and most importantly, one of Starmer's main problems is that he is seen as part of the Londoncentric 'elite' that dominates so much in the UK, but Burnham is more of a 'man of the people'. Whatever the truth of that, these days so much is about perception, and Burnham would be better as a challenger to the threat of Farage. If he managed to redistribute the investment and advantage that London and the SE gets to the rest of the country, a lot of problems might go away. We've heard so many people talk about 'levelling up', but it hasn't happened, and we are reaping the consequences of that now.