This is frustrating, but it has always been an issue; and usually the more you advance in a language tree the more it happens, because fewer people have found the problem and reported it. It’s a human problem that comes with not considering every possibility when creating an exercise. I’d imagine that using AI (in addition to humans) would actually help reduce cases like this, since they could be detected before users run into them.
That’s a bit over the top, in my opinion. I’ve tried plenty of courses, and Duolingo is pretty good to get a hang of the basics of a language.
I’d say, in my experience, the hardest part of learning a language is getting started, and I feel Duolingo is perfect just for that. To get deeper knowledge and become more comfortable, one should probably switch once they start feeling more comfortable with the alphabet (if there is a specific one), and with the basic vocabulary and grammar.
EDIT: Forgot to add but another advantage of Duolingo, is that it’s also great to get a taste and basic feel for different languages; and that can be especially useful for someone who is looking to learn a new language but can’t quite decide on one.
The podcasts and other media consumption will probably be what most benefit you in the long term, and something like Anki and Duolingo I think are good complements for that.
Any alternatives to Duolingo that I think would be worth replacing it, would have to be something that is more focused on the specific language that you are learning, i.e. Nicos Weg for German (and I don’t personally know any for Italian, sorry). Most other general language learning websites/apps would probably be running into the same issues and limitations as Duo, and which one to use depends most on personal preference; however, there is one I’ve heard of called Italki (there may be more) which basically acts as a language exchange app, where you connect talk to people who natively speak the language you are learning, and they can give you input. I’ve never tried it, but I’ve heard good things.
Other than that, you have certified online/in person courses, but obviously those are not as convenient as Duo, and they cost money (probably significantly more than even a Duo subscription).
EDIT: Oh, I forgot to mention, but one thing which I personally enjoy is looking up and trying to read children’s books; and I mean like “90% picture & 10% text” books which are made for parents to read to their very young kids. And as you get more comfortable, try finding and reading increasingly harder books/stories online.