Meh! Might as well lament the death of leaded petrol.
I don't think it's quite so steered by modern correctness as I really don't think the market for shaving sticks is anything like interested in a specific ingredient set. It must be a simple cost versus profit calculation on a product that is churned out by literally millions per year, at a guess.
Back to the petrol analogy. I've not used the veg Tabac, but I do have first-hand experience of Erasmic from tallow to firsrt abominable veg formula to gradually improved and the now really very good formula (although discontinued now as well). I have Boots sticks - vintage tallow and modern veg, so not a direct comparison, but again the veg formula is good! I have both the tallow and veg LEA sticks (again, latest veg stick rather than the abortive first attempt) and consider the veg stick to be better. Given the choice, I'd still take a tallow Erasmic, but would most definitely choose the veg LEA. So, my choice is not so much about ingredients but about the formula. Mind you, LEA has lanolin so not vegan.
Mmmm ... sheep grease!
... and Arko/Derby? Yes, both very good sticks and I also would suggest Derby as the nicer of the two, although Arko is an experience.
Beyond the mainstream, if there is an interest in tallow based shaving soaps then there will be an artisinal market that grows around it. Anyone interested in a really good butcher to soapmaker tallow based soap should look to Moon Soaps.