Featured Images Too Massive

Hello! I’ve been having trouble with my featured images. They show up gigantically huge on the blog post page–a little better on the home page, but still large. I’ve been manually resizing them to fit better, but some just don’t come off correctly. They’re off-centered and/or ginormous.

I tried removing the in-post featured images by updating the single.php file to show no image, but it doesn’t seem to want to actually remove the images from posts.

Is there a way I can get the images to scale automatically or perhaps only show a cross-section of them? It’s ruining my ethos a bit–the little I had as a photographer anyway.

Here’s my site: https://www.slocyclist.com