Maybe I misunderstood, but I don't use a sdcard on my rpi3, it directly boots on ssd.
That said for reliability, or longterm use and possible HA evolution, sure a rpi is not ideal, even the rpi4 could be quickly limited, + tests says it heats more.. (though for the moment usb boot is not released)
Because it depends on what you'll need in future, a NAS storage feature like openmediavault, cameras motion management, a media server (plex, emby/jellyfin), adblocker, IA, voice assistants etc. so many nice services to use. Then a x86 intel/amd solution might be a better solution, a lot more powerful, very well known solution. some cpu have very low tdp but I think this electricity cost variable needs to be compared to the ROI..
maintaining only one server machine might be easier too vs a swarm of RPIs.
- rpi with ssd, no sdcard. nice but limited.
- odroid N2 with its nice passive cooling. armbian. more powerful than rpi4 I think. you need to add an emmc.
- tv box flashed to linux, based on s905x (like the odroid n2), or RK (like the recent rk3399). The advantage is for 70-80 bucks you get a complete enclosed board with up to 4GB ram, at least 32GB emmc, and the power supply. But the inconvenient is not all boxes are fully supported in linux yet, it needs digging. so it's not really a non geek solution
- imho my favorite solution is x86 intel/amd machine, ideally with low noise/passive cooling. some low/affordable tdp, more powerful and evolutive than others solutions. there is odroid H2 based on j4105. you can also find j4105 motherboards for 80 bucks. j5005 motherboards, used servers/proc/motherboard on ebay, mini computers like NUCs or BRIX (some are not really cheap), homemade server machine (my fav because I can pick the exact hw and brand I want).
All solution are nice, like I said it really depends how many service you'll want to run in future