It is quite true that a good many medications need to be stopped or reduced either in actual dose or in dosage frequency ... the reasons for this are that many (if not the majority) of medicines are excreted by the kidneys in the urine, and if kidney function is diminished, the active drug may remain in your system longer and thus the dose or its frequency needs to be reduced to avoid side effects or other damage.
In addition, as the drug(s) are excreted by the kidneys, the mechanism by which the kidneys concentrate the urine during the process of urine formation means that the concentration(s) of the drug (or drugs) is increased many fold as the forming urine passes down the tubular structures within the kidneys ... thus exposing the kidney tissue to concentrations of drug many times those that are safe. This can lead to the kidneys 'poisoning themselves' as it attempts to excrete the active drug.
As I am not your physician - nor do I know your medication list - and it would be wrong to try to advise without knowing your circumstances, I can only talk in generalities. That said, drugs like the NSAID group ... among which are drugs like indomethacin ... can do significant damage to kidneys and are always avoided in people with impaired kidney function. But, once residual kidney function is lost, and there is no kidney function left to 'preserve', it is feasible to consider use them again, always while weighing up any other contraindications or potential complications against the potential benefit they may bring.
In Kamal's case ... see the thread above ... I have been aware - from past discussions with him - that he has been on dialysis for many, many years and has no residual kidney function at all to try to preserve. In that event, the use (or not) of NSAIDs becomesa trade off against any other potential issues - like irritation or ulceration of his upper gut - rather than a concern re what might happen to his now non-existent kidneys.
You, on the other hand, state you still have some residual function ... limited though it may be ... and the preservation of this may actually be useful to you, especially if you still pass a reasonable volume of urine. your stated level of 4% residual function can be a very useful/important additive to the clearance provided by dialysis, especially in patients who are on peritoneal dialysis - perhaps more-so than in those on haemodialysis.
But ... over and above the additional clearance that even a small amount of residual function (eGFR) provides, there is even a greater advantage ... for residual function usually means a preserved urine volume.
Most long term dialysis patients will eventually lose their urine output, but while there is a urine flow (as might be expected with an eGFR of 4), there is also the greater freedom of fluid intake that urine volume brings. This means that even 4% is worth preserving and fighting for ... and any drug that is likely to negatively impact urine volume is still a drug to shy away from, if possible.
NSAID use is almost certain to fairly quickly dry up your urine volume ... permanently ... and this would mean less flexibility with your fluid intake and greater thirst. This is the crux of the problem. It boils down to a toss up between thirst versus joint improvement - if indeed that does occur.
There is no right answer here - and as in all things in life, it comes down to a trade-off. It seems likely your primary doctor has come down on one side of the trade-off, your nephrologist on the other ... and both are likely right - or wrong - depending on your interpretation of what matters most, to you.
I am not sure if I explained that well ... but I think you will get my meaning.