Poco released 2018, August. Maybe this explains what you call a pathetic delay... (face palm)
Comparing on how other manufacturers provide updates you should be thrilled and thankful...
My friend has the global Mi9T here in Australia. He hasn't received an update since October (the Android 10 update hasn't appeared here yet), so your theory about the age of the device explaining the lack of updates is flawed. Besides, the Poco was one of Xiaomi's most popular devices. Rolling out a security patch or two shouldn't be too hard.