I hear ya. I had a Cooler Master Wavemaster case (shown below) that was 100% aluminum and quite thick at that. It was primo back in 2004 (by 2004 standards). It's still in use, but just isn't fit for a high powered modern system.
The biggest drawback of the cases of yesteryear is their tiny whiny 80mm fans. Also, most of them had 2 or 3 fan mounts total. Compare that to modern cases with 120mm or 140mm fans which are much quieter and circulates 3x the air.
What's the benefit of having 2-3x the case volume than you NEED? Back in the day it wasn't a choice you really even had. Then, hardware became more power hungry (and hence produced more heat) but case cooling hadn't caught up yet, so cases got huge to make up for that deficit (and small available hard drive capacity was an issue for a while). These days, with mITX, mATX, and ATX motherboards you can select a case that's appropriately sized for what you need to put inside. There's so much more integrated into motherboards these days and the computing scene is so much more standardized that it's fairly uncommon to need more than a WiFi card (if that, since more and more mobos have integrated WiFi now) and a single GPU as expansion cards in your case. Beyond that, you choose a case based on how many internal storage drives you need and you're done. With the M.2 SSDs (a stick of gum that attaches directly to the motherboard) and high capacity HDDs (4TB costs you less than $100), most systems only need a single hard drive mount. Especially as society migrates toward cloud storage and media streaming (movies, music, games) which relaxes local storage needs.
Something like the Asrock Deskmini at 6.1" x 6.1" x 3.2" can be (technically) outfitted with up to an i7-10900 (10c/20t), 64GB RAM, an M.2 SSD (4TB available), and two 2.5" HDDs/SSDs (say 4TB each realistically) for a total of 12TB of storage. The only thing it's really missing is the ability to house a graphics card. That hardware spec is obviously going to cost a pretty penny (each of the items listed above is ~$500 except for 2x32GB RAM is $225), but the same system can be outfitted with the same CPU you just bought and 2x8GB RAM which would more than satisfy most people's computing needs (browse web, email, MS Office, etc)
https://www.asrock.com/nettop/Intel/DeskMini H470 Series/index.asp
The case itself doesn't usually get kicked around like a soccer ball, so it doesn't need to be built like a tank (which also reduces the cost of the case). Even a flimsy thin metal case with plastic face is going to last 10+ years in most homes, at which point the system inside is likely due for replacement, and there's been 10 years of computer and case innovation/development.
**I'm not discouraging your cause. I actually do the same thing (recycle retired office PCs and donate them to families in need)