Wow, I haven't realized its THAT small. Is it even upgradable with current version of RouterOS 7?
AFAIK it is not (yet) an issue, the biggest current problems are with devices that have a radio due to the new wireless package.
Still, when you buy a new device you usually want a reasonable expectation of future upgradability. In the case of many router devices this is less important, you just set it up, tweak it a little bit and once you are satisfied, you keep it "as is", exception made - possibly - for security related stuff.
If you are some sort of nerd/geek (and you must be one if you are looking into Mikrotik for a home router) it is more probabile that you will want to try new features as soon as they come out, or new gadgets, revolutionary Iot devices and what not, and it might be frustrating finding out that you cannot because it doesn't fit in the storage space or by any other limitation of the older platform.
On the other hand, these older architectures are more tested and - besides possibile bugs that are (hopefully) solved by a new version of the OS - if the router does what it should do now, it will most probably work just fine for years without needing to be upgraded whilst the newer ones might not yet be stable enough and would need more care.