Yes, Murray Road and Railway Terrace are busy at peak times but the present station has decent bus links (which, being realistic, Houlton is never going to match), and there are car parks both sides of the 'tunnel', neither of which I have seen full post-Covid. North side, there's also the significantly cheaper private car park that's as close as Avanti's multi-storey. I would argue that the proposed new station is considerably less accessible to most people living south or south/west of the WCML, which is a fair chunk of the population.
But do they really think a station at Houlton - with just two stopping trains an hour (I suspect unlikely to increase with all the freight the Northampton loop already carries) - is going to drag people over there anyway? Certainly not if you are headed to London.
I live just outside the town to the south-east. In terms of distance, Houlton/Rugby Parkway would probably be slightly closer to home. But there's no way I would use it - under the present timetable/frequency at least.
I suspect you can at least treble that, if not more. We are still at first consultation. There are no firm plans, no funding (and Warwickshire CC certainly doesn't have the money). Nothing more than an aspiration.