I've really given the CSS of my store a lot of laps to correctly align the thumbnails that appear on the main page of my WooCommerce store.
The theme that I use is Ascend from Kaddence Themes although very modified, the css I can not attach it because I use the Google Chrome console
Good morning,
I see that the grill is loaded with Masonry ( link ). This script makes that in the loading of the products the grid fits perfectly in the global calculation automatically, regardless of the height of the elements, but you do not have control of how it does it, since it changes depending on the width and height of each content. It is a very useful script to not denavarse the brains with the responsive layout when you have many elements that fit with different heights.
If you want them to be aligned horizontally, you will have to get rid of this script and use another system by fixed-height rows or be very careful that the "image + description" always has the same height, although this form does not I recommend.
I hope I have helped you. Greetings.