Yes, we all have been burned at some point! But I never blamed martingale for that, it's I who wanted to make fast money and I got busted with some longer losing streak... and just 6 reds on x2 is not a very long streak!
Yeah, you're right that 6 reds aren't a long losing streak at all. For example, my longest losing streak was 18 times in a row when I tried to use a similar strategy on a dice game with a multiplier of 2x on another gambling site.
You are right, 6 is not much, I have also had more than 12 times that I have not been able to win on a 2x shot, 18 times is quite a lot actually, at Betfury it was only enough for me 9 times to lose a large amount of tokens, but the Martingale strategy is not the example to follow, it usually works 1 or 2 times, maximum 3 times, and then to win you must have a large balance, honestly always what I apply the most after winning 2x is to put the multiplier at 3x and I barely win it. I change to 5x until I get the profit, the good thing is the profits that are obtained when you win with a multiplier of 3x, 5x, I think that the martingale strategy can be expanded to those levels and the losses are usually not that devastating.