Another reason for the seemingly not very effective thrust reversers may be that the flight crew is not using them to their full potential in order to reduce noise.
At my neighbor airport CPH
for instance it is forbidden to use thrust reversers due to noise restrictions. What we see there is that most often the thrust reversers are engaged and the engines spooled up to little above idle, only for making a faster response in case of a problem on the wheel brakes. In such a case the use of reversers is of course permitted.
Maybe that is also what you experience?
In the good old days when noise was less talked about, then SAS would sometimes almost pull the tail off their DC-9s, and the thrust reverser really made your seat belt do its duty.
But then I also think that the clampshell reversers on those JT8Ds were more effective than the cascade reversers on modern high bypass ratio engines.
Those old JT8D reversers were also much lauder. First time passengers would often begin screaming of fear for their life when the reversers were engaged. Fortunately the engines were so laud that you couldn't hear the screams.