I'm going to refrain from making decisions on the ideology or quality of the candidate. I'll leave that to people smarter than I.
In terms of strategy, the Dems erred in trying to make this race a national race (to an extent, this is on the DNC and not the Ossoff campaign). The intense national spotlight pushed voters back into their "natural" corners. This goes hand in hand with the pressing need to replace Pelosi as speaker and this comes from someone who has a positive opinion of her.
It, coupled with Trump's win in November and Romney's loss in 2012 should really start to show candidates that simply having the most money and throwing it at ads isn't a winning strategy any more. There's a phenomenon in psychology / advertising that claims that, beyond a certain point, the more often you're exposed to advertising for a product (in this case a political candidate), the less likely you are to buy such product. It isn't even diminishing returns, it's literally negative returns beyond a certain point of saturation.
The oversaturation of ads, combined with the natural partisan lean of the voters pushed people into their natural corner/party and delivered a loss to the Dems.
The lesson for dems should be, we need to figure out a way to reach voters outside of lazy ad buys on tv and radio. But consultants get paid big money and are pretty lazy, like the rest of us. So they go with what has worked in the past for as long as they can. A new strategy is needed.
Democrats suck because of what happens when the parents get involved in a kids' fad?