Whatever issues you have have nothing to do with Adobe intentionally slowing down your computer. That's just nonsense. As to why it's showing you adaptive resolution degradation is anyone's guess, but start by checking your hardware acceleration settings, update your system's graphics driver and flush the disk caches. Likewise I get that feeling you might want to re-read the online help on things like using RAM previews, configuring the caches and so on. If you're running so low on resources all the time then inevitably something is gonna break when there is no more storage space in the cache folders. AE may not even be able to use what you have assigned for the simple fact that Windows itself has safety margins and will simply block apps from using up every last bit of memory and disk space. Again, this has nothing to do with Adobe being spiteful and trying to coerce you into buying subscriptions. You need to straighten out your technical issues and ensure that the minimum requirements are fullfilled.