the whole point of the 6s "meta" is that its the most effective lineup in terms of a time-performance ratio
if you wanna make something like demoknight work its probably gonna take 3 or 4 times as much playtime to get even a comparable ammount of value out of compared to regular demo
you could probably play full time pyro in a lower div too, but if you invested the same amount of time into scout or soldier you'd be a far better player way faster