In my view there are two different things. The regulatory side, which does not care, nor should it, about career progression. And exactly that, career progression.
The regulatory side at the moment does have an age discrimination, especially in countries where the required retirement in airline operations means a lower pension despite having paid the max contribution for 30+ years. And it is even harder to swallow if you can easily pass both your medical and simulator checks. Human beings in general, pilots included, do live longer and healthier, at least in developed countries. An arbitrary retirement age might therefore be the wrong way to go, especially in a time where everything else goes "performance based", from training, over hiring to career progression.
The career progression side is of course not an easy thing to tackle, especially as it is extremely different for many. There are those that join a legacy carrier age 20 and enjoy a mostly uninterrupted career throughout their working life. And yes, those carriers tend do have lower growth and pretty slow career progression, which means any change in retirement age will cause a major change for the normal career of those that are not commanders yet.
And then there are those, that through no fault of their own, have to change airlines several times in their career and/or work in non-seniority based airlines. Getting that retirement fund to where one wants it to be can take considerably longer, depending on when one has to change airlines, personal likes and dislikes of those being in charge of career progression and other arbitrary factors. A possible longer career simply means more time to sort out retirement and the personal problems caused by the repeated disruptions over the working life of those affected.