You can do Anki without translation. My preferred approach is to have "type answer" cards where the question side just plays a recording and then you type in what you heard. I do add a translation on the answer side to let me check whether I understood the sentence correctly, but the focus is on listening and writing in the target language, not translation.

Of course the number of cards is finite, but so are Duolingo's example sentences, so whether you get more or less variety ultimately depends on the size of your deck.

You can, but this is not what someone who just came to it all for the first time and looks for "app I can download and use" will do.

They will download a dect with single words translations rsther then spend a lot of times doing own deck with special features. That is done by people who primarily learn in another way and use anki as memory refresher.

Anki is great memory refreser, but that is not what was asked here.

To your last paragraph, you do set number of cards per day. Even if you have many different sentences on many different cards, they will graduate independently from each other. So, you will still see the exact same sentence a lot rather then getting different sentence each time you see the card.

More important is that practically Duolingo did not caused me to have any particular sentence or translation super strongly burned into my head. Maybe it is variety, maybe something else, but practical result was just not that.