a 1200 dollar prebuilt is, generally, a much better deal than a steam machine if your interest is in gaming. It will have more power, more performance, better repairability, and actual upgradability. We're not talking low spec/budget gaming here, we're talking more about a luxury good, so saying "spend an extra 200 dollars for a vastly superior product" isnt so much of an ask.

If you care more about form over function and want an interesting piece of furniture, then I think thats where the steam machine excels. Its not a powerful gaming rig, almost any 3d game you play made in the past 3 years will probably have to rely heavily on FSR to get decent framerates above low settings on anything higher than 1080p, and any 3d game that comes out after this point will probably be even harder on it than that.. but if you're cool with that and just want a neat glowy black cube in your entertainment stand and can accept the limitations, then Valve has you covered.