If these trading bots were guaranteed money making machine then there would be no need to sell it. The creators would just use it themselves and make large gains. They know it doesn't work half the time and it is essentially useless in a unpredictable market.
You should consider widening your perception of this world.. There is no guarantee in anything, especially in half evolved, unstable crypto market.! When someone makes any guarantees at all, there is certainly a catch! During birth, even a child isn't guaranteed to survive.
Yeah, I don't think the good bots ever really promised to make people profits on themselves. What people were selling and "guaranteeing" were their strategies, using the bot to autopilot. Gunbot I recall distinctly was meant to aim for very low daily profits, based on rapid buying and selling - not something all bots were able to do at the time.
The bot software is one thing and bots do have usefulness for testing (and at time executing) rapid-closing strategies.
You're right! Usefulness of any promising bot is directly depend upon its ability to adjust to any market conditions. The best bot its the one that can offer enough settings / flexibility for a user to be able to deploy adjustable strategies that can be adopted to any market.