Many experts do think they were of little military value. Remember that WWII was the first time humans could attack cities far behind enemy lines. Bombers were revolutionary, but nobody knew how to use them effectively.
They could destroy enemy factories and infrastucture, though unguided dumb munitions were so innacurate that you needed 500+ to destroy one building (IIRC). Modern precision guided munitions work much better, but the Russians apparently are using dumb ones, at least sometimes. But both the Nazis and possibly the Allies thought that they could break the enemy's will to fight by bombing civilians - throughout history, protected from the ravages of war until the armies reached them - into submission. That doesn't work - bombing London didn't drive Britain toward surrender, and bombing Dresden didn't cause Germany to surrender. Bombing/shelling Ukraine won't do much more, unless they just try to kill everyone in the city (unlikely, even for Putin).
IIRC Air force leaders in WWII claimed that they could defeat the enemy through air power pretty much alone, and that land forces were becoming obsolete. It didn't work but they've claimed that ever since - including even for the Afghanistan invasion in 2001.
As we have seen, all the airpower in the world wouldn't stop the Taliban. Bombers are especially ineffective against insurgencies: The insurgents don't present targets, especially ones that linger in the open like a tank division or a weapons factory. And even if you could target a few insurgents, that is a very expensive use of a bomber, its fuel, bombs, etc.