> "if AD and GPO are now dead, what killed them and what are the options?"

The changing world. AD and GPO come from the mid 1990s before pervasive internet, before WiFi, before Cloud computing, before people had multiple computers, before iPhones, before AWS cloud infrastructure, before Kubernetes, before cheap fast hardware for virtualization, before cheap bulk storage, before BYOD and WFH and everything-as-web-app. Before that was the world of isolated 8-bit machines, expensive Solaris workstations and Unix mainframes with expensive admins, and after say 1998 the world was cheap Compaq/HP/IBM hardware running Windows server and Windows 9x desktop, and after about 2003 it was Windows Small Business Server (AD, GPO, SQL, Exchange, SharePoint) and XP Pro desktops.

Cracks started showing when people wanted to logon to a laptop away from the office when it couldn't refresh policies, run logon scripts, talk to domain controllers; when people wanted 'offline files' from a company file share while away from the office, but wanted their corporate email to work when their laptop was online but not pull down company settings over a dialup modem. More cracks when they got a Blackberry or iPhone, more when AppStores appeared and people expect to be able to install whatever they like, more with the rise of Apple Macbooks, with the growth of website based services people can use from anywhere, more with Amazon AWS where company infrastructure is on someone else's premises, more with BYOD and WFH, more with people expecting software to be cost-free, being trivially able to spin up Linux web and database servers because there was plenty of CPU/RAM/Disk and no worries about licensing costs.

> "it’s nice in that admins can’t screw around too much with my system"

If it's a company device, it isn't your system. The company has legal oblications and practical concerns that conflict with your desires as an individual. That might be pushing full-disk encryption or updates, or auto-locking, or restricting use of USB or websites to block potential customer information leak points, or trying to stop you saving work locally that might be lost if the device fails, or trying to stop your device being an entry point for malware or ransomware, or trying to stop you screwing around with their system which costs them employee time to fix and your downtime while it's broken.