We bought our first house and it needs some work, especially the walls. I’m wondering what’s the best way to take care of this horribly patched drywall? We have large sections of wall in various rooms that look similar to the one in the picture. We think it’s from the previous owners DIY remodeling, but they weren’t very picky about their results, it seems. Is this fixable? Or would we need to replace whole sheets of drywall?
Perhaps the previous owners wanted the feel of some personality, or perhaps they shared their personality with the walls.
Since the house is new (to you) and you imply it is yours and you want it to look good - plan to remodel it.
What do I mean? I mean, at the very least, plan to do new sheets of drywall where damage like that exists. It is pretty bad for the one picture you show and the time it will take to "patch in 4 sides" of a new rectangle of size 1'x 2' (just making that number up) may not be much worse in the long run of doing a 4'x 8'.
Not to mention, if you have any incling to change anything, run new wires (AC, HDMI, CAT6??), plumbing, or inspect the insulation, this would be a good starting point.
Getting intimate with the new place and fixing an eye sore.
One way to look at this, if you are inclined at all to learn to do this work, sooner or later you will be sanding. If you replace the drywall you will be sanding the joints. Go get yourself a good orbital sander and go at it on a spot and you will pretty quick learn how feasible it is to repair areas, vs ripping out drywall and starting over. You will need a shop vac too.
If you need to remove a lot of material you may need a belt sander too, but I'd start with an orbital.
BTW when you say "new" house, obviously you mean new to you. If its actually an "old" (pre 1960ish) house you may not have drywall and that's a whole other matter.
Unless you have some other reason to rip it out and replace, you can simply mud that into submission. Get a series of drywall knives (akin to putty-knives, but bigger) of increasing size, a bucket of drywall compound (aka "mud") and go over the holes with the smallest one, wait for that to dry, use the next size up, wait for that to dry, use the biggest one, wait for that to dry, repeat as needed.
At some point it MIGHT be faster to re-rock, but mudding is easy work and not too messy if you take care. You'll have to mud if you do re-rock, anyway.
I have tidied up 40 year old drywall with poorly filled 40 year old nail dents, etc and there's no visual evidence it's not perfectly nice drywall under the new paint. Without some other reason to open the walls up, It was far less hassle to put on enough coats to solve the poor finish job from decades before than to re-do the sheetrock. The main trick is not to try and get it perfect with one coat - using larger knives helps to fill the depressions in layers and smooth the new surface out so the defects disappear.
The pictured area simply looks like a patch that was inadequately mudded by someone who did not understand the basic process of mudding (to restore a finished surface) and simply stopped when the crack was filled up.
Now, if you have wallpaper, that may qualify as an other reason. But I don't see any in your pictures, nor do you mention any. Bad/inadequate wiring or plumbing can be another reason (for removing at least one side of a wall).