I think when answering this question you need to look at from both the perspective of those claiming it and those that in the main pay for it.
Motability was originally mainly for those people who with life changing mobility problems hence the the blue invacar, thankfully times have moved on and better vehicles have become avialable however so has the eligabilty for PIP and hence the the number of people that have access to the motability scheme.
Many people who have life changing mobility issues generally have requirements such as automatic transmission and something big enough to fit a hoist and enough boot space to accomodate various mobilty devices and its almost immposible to find a vehicle now that fits without a 4 figure up front payment especially when the cost of adaptions are added,this is especially the case for claimants that have had conditions from birth and as such have not or are no longer able to work and rely on benefits who find it hard to save the money even with assistance.
So yes I believe the system is no longer fit for purpose when those with the greatest need of mobility vehicles are increasingly have to pay more as percentage to stay mobile.
I can only comment on my personell experience of living with somebody with chronic spinal issues who uses a powered mobility device and who still goes to out work everyday and have seen the choice, avialability and cost continually rising to the point where its debatable on wether its more cost effective for the mileage to lease or buy outright.
As for the general public it is the perception of many that its easy to get a ‘free’ car all you need is a phoney limp or pretend your child has ADHD etc to qualify for PIP and recieve a lovely brand new free car the ‘likes of which us workers could never afford’ is a usual comment and to be honest when 20% of new car registrations in the UK and a whopping nearly 50% in N.I and only 10% of all motability vehicles actually have one or more adaptions fitted you can see how those with no or limited knowledge of the system end up thinking that PIP has become a con and joke and why many politicians especially from the right have jumped on the motability bashing bandwagon, despite the best efforts of many of us to educate them inline the tide is running against us.