Are free cryptocurrency websites legit?

They sometimes are. Faucets serve as a valuable way to get more people interested in new crypto. It's a marketing.

they earn more than what they give you from Ads you make many ads impression before you can get small bits

If u mean faucets, yes, they are, but the "double your bitcoin" once, are def not

As a BTC faucet owner.

The price for you to get that very small amount of BTC is lower than my CPM. I'll make a profit if you visit.

Would making a botnet automatically run faucets be more profitable/undetectable than using a silent monero miner?

Not really they will cam you and take all your money, i know because I run a fake one

I think they don't really exist because in our time is all about the money!

There are faucets, but anything saying "free bitcoin! bitcoin generator! bitcoin hack free" is 100% a load of shit. Its impossible to hack bitcoin like a generator. any legit ones will pay you at mose $0.0001 per click or something like that.

Most make you do things that in turn make the owner of the website money, if you're expecting it for absolute free it's most likely a scam site.