I find it consistently difficult to find good contractors for occasional repairs on our house (yes Swiss houses do require maintenance ).

Each time I contact (reputable) contractors they all have a backlog of several months.

My only conclusion is: Swiss houses are of inferior quality (and they are all busy repairing these houses ), or (and this might be more plausible), there is a lot of new construction going on and have no time to work older buildings.

The third option would be: there are not enough good contractors (lack of competition). But this might be considered normal

Version B is correct. A lot of building is going on, particularily in the Zürich, Basel and Geneva area. And the construction-companies want to get over the rough constructions until end-October and will then concentrate on internal work and repair and maintenance work in winter. And right at present, lots of their workers are on holidays.

Or D, time is relative, nothing happens here within a few months, time horizon in the construction industry is 1-2 years.

Although I would support B to some extent.

You missed the other reason - a reputable builder could never admit to being available at short notice. Even taking a morning dump requires months of planning and reservations in this country.

or the real reason

your jobs are just not big enough, with enough profit in them, for the builders to bother with

This of course may be correct with the larger companies, but the smaller ones will be at your service in late November and in late January and in February.

So that, if you contact them in late October, they will have an open ear to you and give you their date.