Briefly: If you can not get nice pictures with this lens, it's guaranteed to be something wrong behind the camera and not the lens.
Also, the lens 11yo on the neck ..
What it costs to buy secondhand, it is anyway worth it!
I mean, has not that much money to spend on a lens, and want to take pictures of things far away so it's actually good.
You certainly can get nice and sharp pictures with it, however it is a bit more challenging because there is no IS. Plastigt, yes.
But completely worthless, it is absolutely not.
I've had great fun with my 75-300 anyway!
Very easy to get to nice pictures which have the object in focus while everything in the background is blurred, that kind of pictures I like!
The focus motor is quiet and relatively fast, USM version, however, is quieter / faster.
However, one can not take and compare a place like this lens with one that has the IS because it's completely different kinds of lenses, nor against the newer and more expensive then this is a cheap telephoto zoom lens! And for what it is, it's canon!
But of course, do not want to compare it to what it is, so one can cut any product .. One has to be subjective.
Eg 55-250IS is still at least twice as expensive and 7years newer.
The only drawbacks of this lens is that when you have extended the lens so it can feel a little loose and it has easy to hit the maximum level when the camera is hanging down.