the "cubesats" which should have been launched into orbit on Monday are tiny.
Around 10cm sq....
Exactly so. These satellites don't exhibit any of the characteristic features most people expect of a satellite.
Large unfolded solar arrays for power= none. Variety of large antennas for multiple purposes= none. Multi-axial thrust cones for positional adjustment= none.
Your description of them looking like enlarged Rubik's Cubes is very fitting: think of them also as being effectively like smartphones that have been tossed into a temporary unsustainable orbit.
Conventional commercial or military satellites are entirely-reliant upon their propellant-based positional correction systems, and the best shorthand analogy to describe them is as being massively-expensive aerosol cans surmounted by a high-end desktop computer and a cellphone tower.
Once they run out of gas (in the scientific or non-North American sense of that word) they are literally doomed, and have to be either de-orbited completely (Ie brought down rapidly to burn-up in the upper atmosphere) or put into a graveyard parking orbit (which is really just postponing the inevitable).
Most classic non-experimental satellites (such as commercial telecommunications relays for tv etc) actually exist as part of a constellation group of identical platforms, each sharing a closely-defined familial orbital slot.
In recent years (oops, decades) satellite delivery systems could never even begin to operate a commercial/professional system with just one 'bird', and therefore self-rely upon resilient backup satellites that are able to ensure service (the stakes are enormous in terms of cost and operational risk....it must be said that the sky is definitely not the limit!!
Cubesats turn this paradigm on its head, with a much more stick-em-up-cheap-till-they-fall approach. But to provide an equivalently-reliable service (and anything beyond transient regional coverage) you need lots of 'peas' and lots of 'pea-shooters' to constantly provide replacements.
I think that classic Clarke-belt geostationary satellites, in cluster constellations, will continue to be the main reliable mechanism for satcoms, aided by the fascinating (and practical) added possibility of ultralight aerostats (ie stratospherically-located massive circling airframes) in eternal flight, with solar-powered ceramic-rotored electric engines.
I've not had the slightest chance to understand yet how Musk's Starlink system works (launch/lifespan/logic) so if anyone can reliably brief me on that, I would be most obliged.
The failure of the launch from Cornwall saddens me (it's a place I've spent quite a bit of my formative past) but I'm a bit of a realist when it comes to aerospace practicalities (born of long experience). Unless huge sums of money & resource at national superpower level are invested in space-related activities, they will only ever be (at best) faith-based technological hops, as opposed to substantive & sustained leaps.