I’m going to go back on what I earlier said, I would guess given enough time 90% of gutters could be cleaned from the ground with a gutter vac (with a good selection of ends) plus other equipment. The provision is......given enough time
I think how we clean gutters gives the best clean possible in the shortest length of time and this usually means putting the ladders up. We can put them up then use various methods, some times we feed drainage rods the length of the gutter and pull back the soil, sometimes we feed a thin, very stiff high pressure hose along the gutter to liquefy the soil so it runs away or is easier to vacuum we use the same hose to jet up downpipes to unblock them. We tend to use the high pressure hose or rods when they tiles are over hanging too much so access with a gutter vac is not possible.
Over hanging tiles & concealed gutters (where conservatories are built against the home or fitted into a corner) are the reason I believe you can never get away without carrying ladders