does anyone else feel like they have a low stomach capacity?

i've always struggled with being slightly (not terribly) underweight, i basically have no definition and for a 22 year old man, i have the body of a lanky 13 year old. there was a time around 2020-2022 where i tried really hard to find calorie-dense options of my safe foods and incorporating nutrition shakes (ensure and similar brands) into my diet to gain a little bit.

it didn't really work, the root cause of it being that i simply cannot eat enough. even when i'm super hungry after a long day out, i've had to spend an hour drinking just one nutrition shake, and it made me feel super bloated and full afterwards, to the point that i have to skip my next meal/snack of the day because i just wouldn't be able to eat more than half of it. how do people manage to eat so much at once?