There aren't many useful rewards left. The best rewards, like 5% cash back, are either teaser rates or require you to use it at only certain merchants or each month check on the issuer to see what stupid ass merchant they are doing the deal with now, it's a big joke, it's quite literally like having starving people fight over scraps of moldy bread, it's pathetic. A few years ago cards really had some nice rewards.
Sure, most of the rewards on cards now are pretty terrible.
But if you have a card that has rewards, and no fees, it's better than no rewards.
I say, the best advice is to treat a rewards credit card as a debit card.
Don't carry a balance, ideally. If you feel the need to do so, make every effort to bring the balance down to zero the next month.
I'd say use it just like a debit card.
IMHO, there is no purpose for cash these days. Convenience stores and small stores, or small transactions, sure... use cash if so desired.
But make purchases you have the cash in your checking account to cover, that month. Instead of using a debit card, checks, or cash from the checking account, use the credit card. When the bill comes, pay it in full using the checking account.
You'll receive no penalties, no interest, and you'll receive rewards.
Quite a few banks have rewards on debit cards now, but they are a fraction of the credit card rewards.
If you are using the same cash, every month, and paying no interest or annual fees, why wouldn't you take free points? Even if they are small, might as well if you are making no changes to your finances.
Come some time later, especially if you use the credit card every month and pay it off every month, for a majority of your purchases you'd pay up front anyhow - you'll eventually earn a nice bonus gift of free money that you normally wouldn't use.
The biggest thing is to have the discipline to forever and always treat it like a card tied directly to your checking account. Don't get the idea that, just this once, I can make a purchase that'll require a few months with a interest-charged balance. Once you do it once, even if you do make your goal of paying it off in short order, you might slip once or twice. After awhile, it gets challenging to return to 0.