I sincerly disagree with you opinion that enceladus was the last hope of finding life, or even that we have enough informtion on the place to decide if there is or was life there. I'll start with mars which is today a desert of rock with occasional ice,second only to earths moon in terms of inhospitability and has been for most of its history.
Firstly I recommend you read 'temperature dependance of metabolic rates for microbial growth maintenence and survival', which reports findings showing that microbes can metabolise (not reproduce) at down to -40 degrees celcius, which is the temperature of a warm summers day at around 65 degrees north on mars. Secondly remember that in the news quite recently it was reported that volcanic activity may occoured there in the last 2 million years. Microbes have been reliably reported to survive in hibernation for 600,000 years and controversially for up to 250 million. If the last figure is correct then if mars was even as wet as the sahara for ten years in the last 100,000,000 the could be dormant microbes surviving. Thirdly there is a small but unexplained methane source which corralates closely with soil water (bound chemically and ice) abundances. Fourth the ALH8001 blobs of carbon show not that mars had life, but it formed its own complex organics, and important step towards life. The Nakahla meteorite (also believed to be from mars), which ive probably misspelled, shows microspoic tunnels in its center like those bored by rock eating microbes found many kilometeres down on earth. Mars has the sun and volcanic energy (intermittently), It has liquid water on the rare occasions that volcanic activity or large impacts interact with ice, and that water may stay liquid for hundreds of years if the impact is large enough or the volcano erupts for long enough. It also has abundant carbon dioxide, which is all some methanogens need to eat. The normal state of mars is cold dry and sterile, yes, but normal conditions have not held sway across the entire planet for 4.5 billion years without a break! None of this means there is or ever was life on mars, but it means if there was or is it would require a massive amount of time and effort, study of the entire planet down to a depth of kilometers to find it, and if it wasn't we still couldn't be sure we'd not missed something!
Enceladus may or may not have an internal ocean, but if it does it has an energy source, fluid, and hydrocarbons for critters to eat. IF Europa or titan or ganymede, or any other large icy body have oceans there is no reason why acidic conditions should be a barrier to life, plenty of organisms can survive acidic conditions. Titan has abundant complex hydrocarbons to eat, an internal heat source, and possibly a liquid water layer. And if we find Enceladus does have an ocean (more of a lake or sea I'd say), that opens the door to many objects previously considered far to small having one. We could search for a thousand years at the current pace of exploration and still have a thousand years of searching to do before we reach any conclusions. Lastly the absence of free oxygen in the enceladus plumes does not mean that there is no life there, the same as the presence of organic molecules doesn't mean that there is. Oxygen is lethal to many primitive life forms, and not any kind of reliable biomarker. Thats my opinion, and if you want I can email you all the relevant papers and let you decide for yourself how based on science it is. Anyway theres my sincere disagreement. And I suspect I'll regret posting it...