When I first became interested in photography years ago, the prevailing wisdom was to get close while centering the subject in the frame to help ensure none of it got inadvertently cropped. That really wasn't very good advice even then, but it's all too easy to do so anyway. We all do it at times.
Let's suppose you are out with your camera, in search of killer images. Whether you woke up in the dead of night to reach your destination before sunrise, or you leisurely strolled to the site with a pre-made sandwich in your bag for dinner to be eaten before the main action starts at sunset, once you get there, the situation is the same. You're ready and eager to capture the unfolding magic, or at least you'd better be. Perhaps you prefer to wander around actively seeking out that next shot, or you're content to relax and wait, opportunistically snapping away as the magic hour progresses. Either way, once you spot something really cool, you try to get the best images you can, based on everything you've learned and everything that prepared you to be there in that place and at that time.
Zoom lenses make it easy to get in close without even moving your feet. Not that zooming and walking are at all the same thing of course. Getting closer with your feet affects perspective while zooming only changes how the frame gets cropped. But both ways, the bigger you see things, the better they tend to look. I don't need to worry so much about cutting anything off these days since I'm a huge advocate of tripod use (something else I learned along the way). So, I can zoom (or walk) as close as I want and then lock things down to fully consider before clicking the shutter. As such, I end up with a lot of frame-filling shots simply because I can. I'm betting you do this sometimes too, even if you've never really noticed. It's only natural, even if at the same time it may curiously also tend to create images that appear larger than life. Odd, that.
Way back in the film era, one mark of a "professional" photographer was that they shot images with the final framing in mind rather than relying on cropping after the fact. This kept resolution as high as possible since none was thrown away from cropping. And unless you had your own chemical darkroom, cropping to print cost extra. So, there was that. Cropping in Lightroom or whatever your favorite application is undoubtedly simpler today than it was back then, but it still doesn't make sense to throw away any of your megapixels if you can avoid it. Yes, there are many reasons one might lean toward predominantly frame-filling shots.
But the truth is that many subjects will look better if you leave them with a bit of breathing room in the frame. Wildlife particularly benefits in order to avoid the mental "bulls-eye" connotations with the full-on centered option. Even discounting the target overtones, nothing makes an actual wildlife shot look more like you shot it at the local zoo than does zooming in to the max. Even landscape shots can benefit from a bit of extra margin. Or if nothing else, you don't want any undue distractions resulting from haphazard items crossing the edge of the frame. Each one will potentially serve as a distraction to viewers looking at your images in their final form.
Earlier generations of digital cameras with their limited resolution set the price high if you wanted to crop post capture. Full frame resolutions were only just good enough to create results rivaling the old 35mm transparency days. Yes, things improved progressively with each generation thereafter, but expectations went up as well. No doubt at some point you've experienced the amazement of seeing the first results after a significant upgrade to your camera body. Each time you do, it's great, and each time, the bar gets raised further. Nothing less will do anymore.
Yet there have been times, and not infrequent ones I might add, I find myself second guessing my framing when reviewing my images later. As good as some image may be (and no, not all of them rise to even this meager threshold), I realize that sometimes one or two images might look even better were it possible to swing the camera down by a few degrees, or see a bit further to the left or right, or perhaps even rotated differently than the way it came out of the camera. Maybe it wouldn't have been possible in some cases. Sometimes, reframing might cause some other obstacle to thereby swing into view that I had expertly cropped out in the field without giving it a second thought. But sometimes I may have merely defaulted to my training and habit of cropping to final image, depriving myself of having the material available in Lightroom to optimize the framing later. I was already pretty much locked in as far as cropping went based on my choices and instincts in the field.
Now that I'm shooting with a Nikon D850 with its impressive 45.7 megapixels of fabulously sharp detail, I'm realizing that it's time to loosen up and allow a bit more breathing room, so I have more to work with later in Lightroom. It's safe to do so now, even as it honestly no doubt has been for a few years now even if I preferred not to admit it yet. At this point though, I'm willing to risk deciding to cut off a fraction of those megapixels if it means I have more freedom to optimize my composition later at my leisure. I'm OK if I end up with a tad fewer megapixels now and then if it means I can keep my options open and potentially end up with better final images. I'll still have plenty. The cost of post-capture cropping just simply isn't that high anymore. And the benefits are undeniable. I don't want to crop, but sometimes it's worth it.
Now, I have no idea what camera you are shooting with or what the next one you are planning to wow yourself by upgrading to, but at some point, it's worth reconsidering how you frame things. At some point, it's probably OK to start leaving a bit more breathing room. Doing so may go against some early guidance about filling the frame, but that never really was that good advice anyway in every situation. Or at least not anymore.