the less early career academics will assume that they have to work 70-hour weeks in order to succeed
I do not know a single academic in my field who didn't work long hours, to get a permanent position. It shouldn't be that way, but it is.
A majority of female academics in my field don't have children. Those who do have children typically have only one, and had the child in their late 30s, after progressing to at least (tenured/permanent) associate professor. Again, it shouldn't be that way, but it is.
I genuinely don't think it is possible to work only contracted hours (35 per week), take chunks of annual leave, and get a permanent job/progress to professor in my area. This is because the norm is set by people who simply don't work this way, everywhere in the world.
All these things said, it is definitely a choice to stay in this research area rather than side stepping to neighbouring research areas where the culture is better. It would be more realistic to work shorter hours in neighbouring areas of research.
I also agree about using time effectively: working intensively while in the office, clustering meetings together, fixing specific hours for meeting undergraduate and PhD students. I see that many of my colleagues waste quite a lot of time by not doing such things. This is particularly the case for men with wives who run the household i.e. they feel free to be in the office for long hours with somebody else taking care of domestic arrangements.