"Many judges like to use their powers to make rulings on what the law should be rather than is."
This is by design. Its checking the powers of the other branches of government so we don't end up with "tyranny of the majority." Without judicial review, legislators are free to pass any law they'd like without taking into consideration the constitution. No constitution or law can interpret or enforce itself. Without enforcement laws are just pieces of paper. Someone's gotta do it.
Judges have the hard issue of interpretation of laws. Someone is probably going to disagree no matter what they do since every layman has an opinion and laws can sometimes be unclear. Just because your interpretation is different than theirs that doesn't mean that they are nessesarly wrong or trying to legislate. They may even thought they were right at the time but then time proved them wrong and then there must be reinterpretation.
"Judicial activism" is, of course, entirely subjective.
The other thing is times change. One interpretation might have worked 100 years ago but not today. The ethos of a populace are subject to change. New technology comes along. Interpretation can change with it.
Sometimes legislatures go back and try to change the wording of laws after judicial review to make the meaning clearer or to come into compliance of the construction. Or even implement new laws for various reasons.
It is an imperfect system. People are imperfect. They are subject to bias and the accepted values of the time period. The constitution and laws can also be vague.
Some people even think the Constitution is deliberately vague in many area in order to allow it to be a "living document" so it evolves with the times, so to speak. Of course, like most things, this is controversial.
Congress has the power...
"To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries." Article 1, Section 8, Clause 8
This is so vague that it practically begs for judicial interpretation.