wrote:
Its got to the point where its just painful to use in the mornings and
unsurprisingly the vast majority of people bail out at Finsbury and get on
the victoria line putting added strain on that.

Why is it so slow and so unreliable with frequent train gaps of 5 or 6 minutes
the rush hour?

Trains?
Drivers?
Signalling?
Dwell times?
Stations too close together in the centre with too much stopping?
All of the above?

Here's an interesting article about how the Victoria line, with new
automatic trains and signalling, achieves its very high frequency:
https://www.londonreconnections.com/2017/ninety-second-railway-making-victoria-frequent-metro-world/

Maybe, when the Piccadilly line also has state of the art trains and
signalling, it will do the same. But it will still have a route with
curvier tunnels and more stops than the much newer Victoria line, opened
more than 60 years later.