One of the secondary schools I've worked in would have arranged an individual tour for you, and/or an appointment with the SENCO. Another one wouldn't have- due to their intake size and the demographic they served, you'd likely have as many as 500 parents wanting tours (not all of those students would get a place), and in a state school, it's simply not viable to organise this. At the other school, most parents were happy with the open evening (where we tried not to rush them and they could ask any questions they liked) and only around 20-30 parents would ask for separate tours, which is much more viable.
In the vast majority of state schools, teachers have a standard contract which limits the number of hours they can be directed to be in school- this includes any "trapped" time between when they finish teaching, and the start of events like open evening or parents evening. Logistically, there's often very little leeway once you've done an open evening for Y7, one for 6th form, maybe an options evening, plus parents evenings, and maybe one other evening event- e.g. a celebration evening (along with all the other things staff are directed to do, obviously). Most staff don't have the spare "directed time" to be asked to run tours after school, so the only people available to do this are usually those on the leadership pay scale (i.e. SLT), and realistically, they can only do so many tours.
In independent schools, staff contracts will likely specify x evenings, and x days of Saturday working etc, and their pay will be calculated accordingly. This may also be the case in FE in the state sector, too- usually FE lecturers aren't on a standard teacher contract.
It's also worth bearing in mind that state secondaries often struggle to recruit, especially in certain subjects, and teachers tend to value schools where not too many late evenings are required of them.
I do think it's a shame that the SENCOs won't at least arrange a phone call with you at this stage- and actually, that would make me wary- it suggests they're either overworked, or the schools aren't keen to recruit children with SEN. Or both.
I get the evening is inconvenient for you, and that's a real shame, and I understand that having other commitments makes things very difficult. But I do also think your expectations of the state sector are unrealistic, and this might be a bit of a sign that it's not right for you.