As I can see this idea they have of not having fire even if it was set before Shabbos seems to not be a rational interpretation of 35:3 in Exodus.
Some have conceded this to some degree as a site I have on Karaite insights. But their idea of a compromise well today you could use electricity since it isn't having a fire burn. Just admit that you were wrong.
I guess like the Rabbis they can't because it may force people to look deeper into why. Which is a good question? What kind of Shabbos is it to be in the dark Friday night in the winter. That is for God. That is a classic man made type of worship to make yourself suffer and think you are holy.
Overcompensation in one area sometimes is to hide the fact that in another area you are not really doing what you are suppose to be doing. Also they prohibit intimacy between a man and a woman. Which I understand are focus on the Shabbos is not our personal physical needs which we should prepare beforehand.
But intimacy does serve a higher purpose then oneself in possibly creating life. And the torah does not say this anywhere. It did say before receiving the 10 commandments that a man shouldn't draw near a woman (19:15). But that was a special day where that normal part of life should be aside for three days. That doesn't seem to suggest that every Shabbos you should do this. It is suppose to be a complete Shabbos for God. Having relations so there can be another generation I think is giving Shabbos for God since that is one of God's commandments.