I think this is true - Starmer has been a damp squib, Labour isn't exactly innovative policy heavy, and the front bench would be hard pushed to get into the 2nd XI (reserves) - but Labours position is not going to be improved by chopping and changing leaders ever two years.
Johnson's popularity, and Starmers unpopularity, are only inexplicable if you only look to the UK. Crap governments are inexplicably popular across the world, Covid has provided an 'incumbents haven', and whether it last for another 6 months, or two years, or 5 years, I think it just has to be weathered, because I don't see much apart from time, and self-inflicted events changing it.
I think Starmer ought to tack left on some of the economic stuff, but I don't see that having any immediate/medium term effect, but it would be a sensible policy of getting the public used to hearing this stuff long before the next GE.