Born and bred and still living in Northampton.
Going to echo many of others comments, Northampton town isn’t great but i visit about 1 a month if that and in many ways who uses town centres much these days any way?
MTBing is not great but ok with Harleston Firs and Delapree Abbey being good fun if your with locals, check out the local MTB club Tredz.
if you head out of the town towards Kingsthorpe, Pitsford and Old village then you have some fantastic villages with stunning cafe’s hidden away and some great pubs serving dam fine food. The roads out that way then stretch into Leicestershire and Rutland which i strongly believe are some of the nicest road riding you can find in the UK. I can easily clock up 1000 meters of climbing over 55 miles. Also great lanes for a CX bike with lots of Bridleways and tracks around reservoirs.
All in all yes Northampton has its issues but what town doesn’t, but i have no interesting in moving and love what the area has to offer.
If you have any questions then drop me a line at any point.