It's not perfect or anything, but it's usually a step up[1], and the funniest thing is that GPUs generally had less of ... "interesting" compute facilities to jump over from, just easier to access usually. My first 64 bit laptop, my first android smartphone, first few iPhones, had more MIPS32le cores with possible DMA access to memory than the main CPU cores, and that was just counting one component of many (the wifi chip).

Also, Hyperthreading wasn't itself faulty or "bugdoored". The tricks necessary to get high performance out of CPUs were, and then there was intel deciding to drop various good precautions in name of still higher single core performance.

Fortunately, after several years, IOMMU availability becomes more common (current laptop I'm writing this on has proper separate groups for every device it seems)

[1] There's always the OpenBSD of navel gazing about writing "secure" C code, becoming slowly obsolescent thanks to being behind in performance and features, and ultimately getting pwned because your C focus and not implementing "complex" features helping mitigate access results in pwnable SMTPd running as root.

Relatively common nowadays. It used to be delineated as a feature in Intel chips as part of their vPro line, but I think it’s baked in. Generally an IOMMU is needed for performant PCI passthrough to VMs, and Windows uses it for DeviceGuard which tries to prevent DMA attacks.