Isn't atheism based on the argument from ignorance FALLACY? (see below)?

Sorry, no cigar. Atheism is based on plausibility. Is it more plausible that the God of the Bible exists or doesn't exist? If you take the evidence from the Bible and define God according to it, it is implausible that he exists. If you take the Bible in context with the other religious texts, it is no more plausible than the rest. If you look at the application of the Bible throughout its history, it is implausible that its followers believed in the same God that is worshiped today. Atheists don't believe that this God doesn't exist by default, they believe he doesn't exist because it is too implausible.