That's what they said about hot jupiters. Exoplanets could have been detected decades earlier had there not been a consistent bias against the idea of large objects orbiting so near host stars, a bias based on a single data point (our solar system).
Hot Jupiters and CFCs are very different things. Hot Jupiters were puzzling but something that could be readily detected by existing instruments. Once discovered solar system development models were improved.
CFCs in a planet's atmosphere is something current instruments can't detect. Even if they could the number of observational candidates is limited. The only way we could detect CFCs is if some civilization was actively producing them at the time that light left the planet. So even if there's millions of CFC producing civilizations in the galaxy the odds of detecting those CFCs in candidate systems is extremely low. Even if those civilizations produced CFCs for millennia the odds are against ever seeing them. So it's pretty wasteful to use valuable telescope time for that rather than something that has a higher probability of giving some results.
It's not about solar system chauvinism or biases. There's not infinite amounts of science money or science time. No one is writing off unlikely events, it's just breathless searches for those unlikely events has a huge opportunity cost. And talking about biases, assuming technological civilizations will produce CFCs is a very Earth/Human biased assumption. CFCs were/are produced on Earth for market reasons that don't necessarily apply in any circumstances except those that worked out on Earth.
Ya, but if people were allowed to look for hot jupiters in the 70s/80s they would have found the first exoplanet far sooner.
I think the other poster might be alluding to a chicken-and-egg situation: could a stronger theoretical basis for the existence of 'Hot Jupiters' have driven development toward the goal of their detection 20 years earlier?
So until Hot Jupiters were discovered they were not predicted. No one even thought to look for them. No one was thinking about Hot Jupiter detectors that just didn't get funding.
Had billions of dollars flowed into astronomy instead of particle accelerators exoplanets (of all types) might have been discovered earlier. Then again they may not have. It's a pointless "what if".
We have spent tons of money on particle accelerators to no clear benefit, either to science or to society. If a similar amount of money had gone to SETI, many of the above objections would have been addressed and resolved, with the advantage that science is being done which the average person paying for it is likely to a) understand what is being asked and b) be interested in the answer.
Particle accelerators have exploratory experiments like hunting the Higgs boson with LHC but they run lots of other experiments as well. There's also lots of particle accelerators (of varying capability) around so if you devise an experiment needing one you likely have several options unless you literally need the LHC.
With large telescopes there's far fewer available and the sky is pretty big. Radio SETI is a long shot search and optical SETI even more so. It's not that they lack merit but getting funding for telescope time is a lot harder when the chance of any positive finding is very remote. A lot of SETI funding actually piggybacks on other research using the same telescopes.
The chances of SETI finding positive results isn't necessarily from a lack of things to find but from physical limitations. Our best radio telescopes could only detect Earth's more powerful radio emissions from a few light years away. Broadcasts like TV and radio wouldn't be detectable outside the solar system. The inverse square law is a stone cold bitch for interstellar communication. SETI's best hope of finding signals are ones intentional ones.
Even with billions of dollars SETI would have similar chances of detecting an ETI as without. It's a needle in a haystack search with warehouse sized haystacks. More money doesn't necessarily get it done much faster or better. There's a limited number of sites for large radio telescopes and they have limited fields of view and stars are only in that FOV for a limited time. More money might let you search the warehouse sized haystack a few times faster but it's still a vast search space.
So you devise an experiment to measure oxygen absorption that uses a probe's existing mass spectrometer. Your experiment doesn't cut into the probe's mass budget so it basically is just a scheduling issue. If your experiment is bumped from the mission schedule there's not compromising the probe or total mission. You've got a pretty good chance of getting that experiment on the docket.
This is contrary to a nutrient experiment that eats into the probe's mass budget and mission time. If the sensors are dedicated to the experiment that's less mass for other sensors. Even if you got approved if you can't built the experiment to be reliable and survivable it won't get approved.
Similar is true for trying to measure CFCs on exoplanets. There's a handful of instruments that can even get spectra from exoplanets and even then only from transiting ones and even then only has giants so far. Even if we could detect CFCs in terrestrial planet atmospheres, CFCs do not stay in the atmosphere very long so you'd only detect them (from a technological civilization) for a very short window of time. The odds of finding them are vanishingly low with current instruments. No one is going to return your e-mails if you propose observations of CFCs because it's a snipe hunt wasting valuable and limited instrument time. If you're a serious researcher you'd know this already and wouldn't waste people's time. Methane is a general purpose biomarker and is something far more likely to be found. Since you've got a limited stars you can even gather information from the time is better spent on the more likely observation.