I'm undecided as to the merits - or not - on whether Starmer should be pushing for a rise in corporation tax or not. The obvious point to make is that is wouldn't affect small, struggling business during lockdown as corporation tax is a tax on profits, and if you're not making any money (let alone profit), then... Also, again obviously, the UK has a very low level of corporation tax compared to other countries (it was an attempt by the Conservatives to "try and do an Ireland" and encourage overseas businesses to move here - hasn't really worked as anticipated) so there is plenty of slack to implement a modest rise in corporation tax.
But the economy is still fragile, and the impact of Brexit really isn't understood as any potential damage which may have been caused has been masked by the Covid pandemic. And interest rates are very low and there is still plenty of slack available for the Government to borrow more should they need to. I think there is a genuine case for a rise in taxes, but I really think this can wait until the Autumn budget: if we're in a situation where we're still arguing whether to increase furlough schemes, and various industries are still looking for more cash to tide them over then now is not the time to start addressing taxation. We can wait a few more months. And I think taxes will rise in the Autumn - word on the political grapevine is that "dishy Rishi" is wanting to do this, so that he (or his successor) can announce lowering of taxes again before then next General Election.
As for Starmer himself - I still like the guy, and I think he is the right person to move Labour forward. I think he's struggling at the moment as Boris is riding the wave of popularity with the success of the vaccine rollout, but on the whole he's done what the leader of the opposition is supposed to do in a moment of national crisis: give guarded support in the Government in trying to get the UK out of this mess, and continually - and constructively - point out the flaws in Government approach and offer advice as to what should be done. But you only have to see that stats and data he gives out in PMQ's that he's building up a lot of evidence against the Government and when the time is right, challenge the Government on all of these. However, I think he may struggle in a packed House in PMQ's with all those Tory baying hounds behind Boris - he is more suited to a courtroom.