The RA4 process is an industrial process for mass produced color prints, and has very little room for variability. You can't really control contrast, since there are no variable contrast color papers available. You can change the overall color balance by changing filtration, and you can still burn and dodge, Traditional color printing via this "wet" process has never been easy, and has always been expensive to do at home. There are many things that can go wrong, but the lens is the least likely problem.
These days, color film is usually scanned for digital inkjet printing. Even if you go to a commercial lab now, the prints will be inkjet digital prints, not the RA4 process. There are many advantages to this approach, since you can easily manipulate your scanned digital image in software such as Photoshop and others. The software give you the ability to change contrast, color curves, and many many other things, that would be almost impossible to do with traditional "wet" processing.
I would suggest taking one of your negatives to a commercial lab for printing, to see what kind of result you could expect. You can then compare that to what you've been able to get from you own developed images, then decide. It's hard to know if what you have now is a problem, it you have nothing to compare it to.