It should be means tested
Perhaps, though that does introduce more complication of course. Plus those who contribute more in tax might via earning more might, not unreasonably, question even more what's the point of their contributions if they cannot even get disability support. Many of them are already locked out of a previous universal entitlement in the form of Child Benefit. But means testing is a valid consideration. I'd just question where you set the limit.
and have a much, much stricter qualifying criteria - which the Government was obviously planning to do until the left wing Labour backbenchers got involved.
The qualifying criteria are, already, strict. The Daily Living criteria are
here and the Mobility criteria can be found
here. There's various other factors to consider beyond just the plane text reading of the criteria (for instance you have to not be able to do the activity for 50.1% of the time, it has to have affected you for three months and will last for at least another nine, you need to be able to do things safely, to an acceptable standard, repeatedly and in a reasonable time period) but we don't need to get too dogged down in that detail. From those activities you need to score eight points to qualify for standard daily living/mobility and twelve points for enhanced daily living/mobility. No double counting, you can only score once for each activity and you can't count points scored for daily living to help you qualify for mobility or vice versa.
So lets take a person that might have osteoarthritis in their hands, knees and shoulders and is in their 50s. Perhaps they've been a nurse or maybe they worked in construction or similar, something that's put wear and tear on their joints anyway. That likely means that their grip strength is going to have been impacted in their hands. They'll find it harder to hold onto knife to peel/chop up food, to grip a potato, or lift a pot/pan to or from the hob. Depending on how bad it is in their knees standing might be an issue. Liklihood is that they'll need to use some aids around the kitchen, perhaps electric tin openers, stick on chopping boards (where you can stab the item onto the board), perhaps chunky grip pans and/or lightweight pots and pans. Perhaps even a perching stool. That would score two points for needing to use an aid.
They might need to use chunky grip cutlery to be able to cut up cooked food on their plate for the same reason of having dodgy grip in their hands. That would be another two points.
Looking at washing themselves again with their shoulders they might find reaching above head height is difficult so would struggle to wash their hair, it might also be hard for them to stand in the shower for long enough so a shower stool might be required as well as getting in/out being risky due to their knees so grab rails might be appropriate. That would be another two points.
Manging the toilet it's likely that their knees are going to make getting up/down from the toilet tricky so likely that a raised toilet seat would be needed and possible some grab rails as well to help steady them. That would be another two points.
Finally depending on the severity of the arthritis in the hands it could be that manging buttons, zips and shoe laces will be difficult. They might find that they have to avoid certain clothes. It might also be hard to raise their arms above their head to put on t-shirts or jumpers. Bending might be an issue depending on how their back is. It might well be that they have to use slip on shoes, clothes with either no fastenings at all or with chunky handles, or it might be that they have to go very slowly whilst dressing to accommodate the pain and stiffness (especially first thing in the morning). Likely that they would need another two points.
That would give us ten points for daily living and an award of the standard rate. So this person who struggles to make food for themselves, to cut up food on their plate to wash themselves, to get on and off the toilet and dress themselves currently qualifies for £76.60 per week of extra money. To qualify for this money they've made a phone call to request a form, the form has arrived (around 50 pages) and they've answered detailed questions about some of the most intimate matters going that will be read by strangers, they've then taken part in an assessment with another stranger (a healthcare professional of some description often a nurse but could be a physiotherapist or even a paramedic on occasion) where they've been asked to talk to them about those same intimate matters in as much detail as possible (they will ask how you manage to go to the toilet, they'll want to know how you manage to clean yourself after you've defecated, how you manage to get/up and down, if you can get there on time and so on), after that the report produced and forwarded to the DWP to make a decision on your entitlement.
It is not an easy process. It certainly is possible to game it. But that isn't because the criteria are too loose but because the quality of assessment is, frankly, appalling. We have created a benefit with quite reasonable qualifying criteria then designed a system which is so awful people who are entitled feel as if they're been interrogated and disbelieved whilst the few charlatans (they do exist, but not as many as people like to imagine) that are happy to lie through their teeth can secure an award. You want to fix PIP? Fix the quality of assessment.
Oh, and the proposal that Labour had to tighten the criteria would have meant the above person wouldn't have qualified for PIP anymore. I'm not sure someone who struggles to make food for themselves, to cut up food on their plate to wash themselves, to get on and off the toilet and dress themselves is the kind of person that we should just be kicking off PIP.