But if they keep it updated for modern systems that means as time goes on the files they are offering to install... won't work on old hardware because they've been updated to the modern era.

Sure if you grab a file from them and never get a newer, more maintained version, it will play on exactly the hardware and software you had when you bought it... But if you lost the install file somehow and went to grab a new copy five years later the updated ones may no longer run on your old hardware