But it essentially becomes a fishing expedition, and that is what the 4th is supposed to prevent.
So you go from "gee, sir, you made a bad lane change" to "well, let's see, why don't we hold you until something we have no probable cause can be investigated". They can escalate this kind of thing really quick, and go outside of the law.
In a world in which police can steal your money without oversight of the court by saying "well, he had cash, and we thought it might be drug related (wink wink) so we took it" ... if you don't put checks and balances on the police it's worse than not having them in the first place.
If your police can participate in shake down rackets to try to find cash they can claim was the proceeds of crime, and have a drug dog check you on the basis of a traffic stop with no other probable cause ... then it's time to start shooting the police, and saying "fuck it, we'll live in anarchy".
When the police don't give a crap about the law, it's time to stop respecting the police or pretending that they're doing any good.
So, I say "fuck the police" if they're just there to fuck us. Failure to follow the laws says most police are inept, or crooks.
And if they can't weed out the bad ones in their ranks, then it's time to assume they're all crooked or incompetent, and force the bastards to wear body cameras 100% of the time. Because, really, you simply can't take the police at their word any more.
You sure as fuck can't count on them to properly interpret the law.