Things I learned: River sand is the best type of sand to use in Concrete. There a companies that manufacture sand. Desert sand is too fine to work well in concrete. There are "sand mafias" in India stealing entire riverbeds of sand.
If it's washed and clean of dirt...maybe. But crushed stone IMO is even better, it's not round and thus performs better in earthquakes.
Maybe if you manage to pump the concrete with a reasonable wear to the equipment, you mean.
Normally with crushed sand you need to increase cement quantities (because more water is needed) and need finer fillers like "flying ashes" and since you dont' want to have excessive resistance and thus excessive shrinkage, you need also other chemical additives.
And - just for the record - rounded aggregates tend to make stronger concrete, not the other way round, not because of the "surface", but because of the "shape", a concrete made of only spherical (in theory) aggregates has the less voids, and the more the actual shape of each aggregate tend to be similar to a sphere the less voids you find in the mix (that need to be filled by smaller fillers).
Of course this is "generally speaking", concrete is a product not much different from cooking, you need good ingredients, a good recipe, good equipment and a good cook to have a valid result.
I am amused when YouTube video presenters claim they didn't have enough time in their film to include a key important aspect. In the days of broadcast TV programmes would have a fixed time slot and some content might have to be edited out or not covered. Rarely did any presenters say 'not enough time' though. But on YouTube where there is 'plenty of time' and a video does not have to be a particular length, people do claim 'not enough time', to make you watch ~10 minutes to learn nothing much beyond how you must like and subscribe to their channel.
To present a topic properly takes much more time than the 2 minutes you see in the video.