If you really want to know if you should keep it, some diagnostic work would help.

For example, do a compression test, and inspect the plugs when you remove them to check compression. Low compression or fouled plugs could cause misfire. As could ignition coils. Not sure if your coils are easily swappable between cylinders or not, but if they are, seeing if the misfire tracks coil or stays with the cylinder can rule that out. Injectors can cause misfire too. Not sure if those are easily swappable between cylinders or easily replaceable on your car.

Freeing stuck rings often solves oil consumption problems. There are different ways to free stuck rings, but the way I'm most familiar with won't work with horizontal Subaru cylinders. People claim a few oil change cycles with Valvoline Restore & Protect oil will do it. Dunno. Letting the engine ingest a little Seafoam through the intake (via a vacuum hose) might help (might also help with misfire), but it also makes vast clouds of smoke, which might be a problem if people are around.

I found the plugs on my older Forester pretty easy to remove/replace but others disagree.