I've had a synology since 2015. Why, besides the drives themselves, would most home labs need to upgrade?
I don't really understand the general public, or even most usages, requiring upgrade paths beyond get a new device.
By the time the need to upgrade comes, the tech stack is likely faster and you're basically just talking about gutting the PC and doing everything over again, except maybe power supply.
A 80Bronze 300W can still be more efficient than a 750W 80Platinum on mainly low loads. Additionally, some of the devices are way more efficient than they are certified for. A well known example is the Corsair RM550x (2021).
If your peak power draw is <200W, I would recommend an efficient <450W power supply.
Another aspect: Buying a 120 bucks power supply that is 1.2% more efficient than a 60 bucks one is just a waste of money.
Understandable... Well, the bottleneck for a Proxmox Server often is RAM - sometimes CPU cores (to share between VMs). This might not be the case for a NAS-only device.
Another upgrade path is to keep the case, fans, cooling solution and only switch Mainboard, CPU and RAM.
I'm also not a huge fan of non x64 devices, because they still often require jumping through some hoops regarding boot order, external device boot or power loss struggle.
I don't really understand the general public, or even most usages, requiring upgrade paths beyond get a new device.
By the time the need to upgrade comes, the tech stack is likely faster and you're basically just talking about gutting the PC and doing everything over again, except maybe power supply.