Just to add my 2c
I think there are a few reasons people fail to get there elbows under the bar
1. is that they’re using their arms to rotate the bar.
2. The weight is too light so they’re not really having to ‘catch it’
3. The bar is not moving in a straight line close to the body
I remember when i was learning i’d use an empty bar to warm up with and just
Think of the bar as only being allowed to travel in a straight line and it was my job to get underneath it, i’d forcefully drive my elbows up hard once i got under the bar, this really paid dividends and while by no means am i a great oly lifter i’ve never had problems with my elbows since