These are all very concise and well-explained reasons to keep your desktop.
You, u/T900Kassem, can also use the old desktop as a media server with the GTX 970 for H264 transcoding (not sure about H265, Intel Arc would be a good upgrade for that), or as a home theater PC for playing games or replacing an array of consoles with emulators. Those systems are also fun to mess around and tinker with using expansion cards. For example, I'm using a cleaned up 2009 Mac Pro with a spare GTX 745 I had lying around to experiment with virtual machines and PCIe passthrough.
You can re-purpose the desktop for many more use cases than even a Framework laptop. Look at the r/HomeServer subreddit for more examples. Some include using it still as a gaming system with even a $200 GPU upgrade (like an RX 6600), a media server with some inexpensive hard drives, a home server running backups or services such as pi-hole, or just as a system to experiment with. I have a desktop with a Ryzen 5 3400G and 2 PCIe x16 slots that I would use to experiment with PCIe passthrough. That experience would have been far more difficult with a laptop due to the proprietary configurations used for laptop motherboards, and the difficulty in managing screen outputs even on a laptop with two GPUs.
My point is that even if the Framework laptop is faster in certain workloads for you, this can easily be alleviated with an upgrade to some of the desktop's components. Even without an upgrade, there are many possibilities for you to still use your desktop which, honestly, still has decent components for a variety of use cases. I'd love to use that system as an emulation PC.