Hi,
I believe we’ve discussed about this through the support service.
For anyone else having the same question, TwentyTwentyOne filters each image’s attributes (including products) and adds inline styling to set the maximum size attribute. We don’t do this in our themes because inline styling is generally bad practice.
If (all) the product images used are rather small, it should be possible to force shrink them with CSS:
body.woocommerce div.product div.images img {
max-width: ...px; /* actual image files width or of the smallest of them */
}