Couple of points here to unpack.
What do we mean by “useful”?
For comprehension practice and/or vocabulary acquisition?
Or just to get a sense of the sounds.
I’m no expert though I have successfully taught myself Spanish to an advanced level of fluency and I’m likely around middle intermediate in French.
I have watched a ton of youtube videos recently by polyglots trying to see if I can grab insight in how to QUICKLY go from intermediate to advanced.
One of the polyglots swears by something called “shadowing”. There is scientific research to show it “helps”.
Shadowing is just simply listening to the foreign language spoken and attempting to copy it without understanding it. Allegedly this assists in comprehension down the line as well as pronunciation.
I agree with others in this thread that if you don’t already have sufficient vocabulary just trying to listen in and of itself might be very difficult to do with questionable benefit other than maybe getting a sense of the sounds, rhythm and cadence but again I have no personal experience to back it up. I haven’t run the test myself by listening to either spanish or french for an extended period BEFORE I WAS READY.
What I do do is check in from time to time before I am ready to try to see how much I can understand. Usually I find it painful.
What I have found in both cases is for me there is a breakthrough level of vocabulary. It’s around 2,000-3,000 words of brute force memorized vocabulary lets me understand some of basic spoken material. By 4,000 words I can get more than half sometimes nearly all and I can make a guess what the missing words mean.
My experience was first with French. I tried brute forcing the words in French written in a product similar to anki (supermemo). Although I successfully memorized those words (several years ago) I failed completely to be able to understand any spoken French even after several thousand words.
My second experience was with Spanish. I did the same technique but I was able to understand some spoken Spanish after it. My hypothesis is that Spanish is written very similarly to how it sounds so I had an almost-accurate sound representation in my memory of the spoken Spanish. My ability to understand some spoken Spanish after brute forcing the vocab list encouraged me so I continued with just listening to Spanish music, spanish radio and watched a ton of telenovelas. After roughly a year I found myself essentially fluent in Spanish. That was more than ten years ago.
I tried again with French about two years later using the same technique and failed again.
This time around I used google translate for each of the words in my vocab list which took about three months, recorded them and converted them into individual MP3s. Then instead of using written French I used the spoken french MP3 words. This time it worked. I found myself able to understand some of the French spoken input. With this encouragement I started watching a bunch of French youtubers. Then I was looking on youtube for polyglots to see if I could figure out how to get to advanced from intermediate without having to just watch a year worth of television and I found Steve Kaufman.
I believe Steve is mostly right. He is wrong IMO in one area: brute force SRS is very helpful to accumulate enough vocabulary to GET STARTED but in and of itself it won’t make you able to speak the language.
I believe that lingQ in particular has solved the “administrative” problem of locating additional vocabulary/unknown phrases out of a stream of text and this will speed up by some percentage the process of moving from intermediate to advanced.
This, however, is only my hypothesis. It might be that I am getting some large chunk of benefit from already being fluent in Spanish. I’ll test the hypothesis later in the year when I start Russian.