An RPi as a desktop computer ?
I'm sure that the latest generation can be used as a desktop computer, but I am also quite sure that it is not a desktop computer.
At least, not compared to mine.
And, when I check the specifications, I can see the difference.
The CPU is a quad core 1.5GHz thing. Respectable, but an i7 6700 trounces that without breaking a sweat.
The RAM can go to 4GB, and it is DDR4 - congrats. I have 32GB.
The Pi has Gigabit Ethernet, just like mine.
As for video, I have a MSI GeForce GTX 980 TI LIGHTNING with 6GB of DDR5 RAM. I doubt the Pi holds a candle to that.
That said, the Pi 4 has one great advantage over my rig : it can apparently operate on a 2.5A power supply.
That's not enough to turn on my CPU.
So, the Pi is undoubtedly a respectable little thing, and if Apollo 13 had that, they would have had less energy problems and largely enough computation power.
But it is definitely not a desktop.