To be fair to Brown, his initial reaction to the 2008 crash was QE, zero interest rates and austerity, and I think the 'consensus amongst economists' is that this put a brake on the crash at a time it was desperately needed, and he's been pretty well praised for that.The problem with New Labour in government wasn't that they spent too much money per se, it was that their way of funding that spending was fundamentally flawed and unreliable. They geared the economy around the finance sector and service industry at the expense of more resilient sectors like manufacturing, and built their spending plans on the assumption that the finance sector would remain stable and continue to grow indefinitely. Unfortunately, whilst tying our fate ever closer to that of the financial sector, they failed to put in place any safeguards to prevent it from fecking itself and us, despite the fact that it has reliably done so at least once every 20 years since the start of the 20th century.
To my understanding, the overwhelming consensus amongst economists is that austerity measures under Brown and Cameron impeded our recovery from the 2008 crash rather than aided it. For whatever reason, barring the Corbyn years, Labour has spent 15 years ignoring that consensus and insisting that the lesson to be learned from New Labour was that spending money is bad, when the actual lesson was that its bad to create a situation where the state of your economy is largely dependent on whether rich people gambling with other peoples' money decide to do so responsibly.
Would Brown have just continued with austerity for another 15 years? I very much doubt it given his record on maintaining growth, but I suppose we will never know.
As for his reliance on services and failure to invest in manufacturing I totally agree. I don't think we've had a government interested in manufacturing since Wilson really, and whilst Corbyn used the term investment a lot don't think that's what he meant.