Corbyn was a terrible leader for Labour. Regardless of what you thought of his policies, the man was terrible at communicating and never made the effort to reach out to people who didn't agree with him (the people he needed to win elections). Blair did the opposite by moving Labour to the centre ground. Starmer is trying to emulate that strategy.
Corbyn also hated the media. Rightly or wrongly, you need the media on your side otherwise they will only display you in a negative light. Blair was very clever to get the support of Murdoch, Starmer seems to be doing the same. You can't win an election with the entire press against you.