The effectiveness of stealth is another one of those sword/shield things. At first, the advantage went entirely to stealth planes, because since no one knew about them, no one even bothered to try to find out how to find them up there.
Time passed, and the balance began to shift slightly in favor of radar, if you consider only large permanent ground based radar. Low profile returns can be detected, and higher power helped some. But, the radar power problem hits a wall fairly soon, because you can’t look at everything, and everything returns some radar, even subtle differences in the temperature of the air itself. Also, it doesn’t help to illuminate a target if the illuminating radar itself is the first target.
So the balance shifted back to stealth as better radar absorption and deflection refinements brought the power level needed to a point where it was pretty much pointless to spray megawatts at everything, if you couldn’t pick out the targets from the noise. That lasted a while.
Computer power is now the main problem for stealth. As the processing power of small station computer systems improves, a small portable radar system is able to decipher more and more noise obscured data into targeting information. And, just like everything else about computers, what was prohibitively expensive last year is only wildly overpriced this year. Next year it will be on sale at bargain prices. Stealth on the other hand doesn’t seem to be coming down in price on the same curve.
So, the multibillion dollar stealth plane of the future could be in danger of being defeated by the hundred thousand dollar mobile radar system of the future. Also, miniaturization will allow mounting such systems on planes, and eventually air to air missile systems. Those will cost a million or so a pop, but two or three of them might cost you a six billion dollar attack aircraft. It’s and expensive way to fight a war.