I dunno if it even needs to be difficult; even a bit tactical would change the nature of the thing. As it is the mobs in these things tend to be mindless converging waves; what if they set up set pieces, ran for help, dived for cover, used supporting fire etc etc?
Also perhaps overambitious, but what if the difference between low and high level enemies wasn’t their HP or damage, but how tricky and organised they were? What if leveling up didn’t make number get big, but instead gave you more options in a fight?
If someone came into my home and started making derogatory racist remarks about me, I’d say that response would be entirely appropriate.