Safari on my iPhone is basically unusable. Refreshes the page constantly; swipe back a page and it refreshes; scroll down long enough and it refreshes. Then there's Reddit - crashes constantly, literally will not load comments. It does this with and without extensions.
Sounds like you’re on an old phone? I did have RAM issues on the 11 Pro that unloaded every app as soon as I opened the camera, but otherwise tabs did not unload that often.
Reddit is its shitshow and I ended up installing Apollo. This is not Safari’s fault.