I think I am right in thinking that pax tolerance to tech stops is better in the early days such as 60s and 80s but goes down in the modern era.
Doesn't appear to be the case.
The biggest issue with this is that the demand graph is essentially off by 50% or more. If I look at a route that says 400 daily pax, and I stick a 300 seat plane, most appropriate to that route, on it, then when my RI and CI are high, competition is non-existent, I should get close to a full plane. But I don't. In fact, I get half the stated demand, or even less.
The problem isn't whether a ULH flight should be profitable, whether default pricing should be different (that's an entirely separate argument), the problem is whether an appropriate plane/s on a given route should be able to get roughly 100% of displayed demand when RI is 100, CI is 80+, and pricing is at the default. And right now, that doesn't happen. Players shouldn't be expected to look at the displayed demand, listed as 95% accurate, and instead treat it as being more than 100% optimistic compared to the true demand. Tech stops should only get penalised if there is a competing, direct flight.
At least until some future point where there is a much more complicated algorithm, and a virtual pax wanting to get from MLB-AMS has the same sort of options as RL, a 'direct', tech-stopping flight, or a connection in SYD, LHR, DXB, etc.
Just another example from the current JA. Amsterdam-Delhi with tech-stop, daily demand is in the low 60s for Y-class. RI is 100, though CI is only 30. I'm selling 22 seats/day, just 1/3 of demand. Amsterdam-Miami, daily demand is ~120, daily pax are averaging just 43, with a low of 27. Again, roughly 1/3 of the displayed demand, flying an appropriate plane on a route that pax should expect tech-stops on. At least I'm selling 100% of C-seats for the week, with 4 supplied and ~20 demand.