It's unlikely many types of exoplanets could have been detected "decades" earlier. Transit and Doppler detection methods require good seeing power and accurate intensity measurements. It takes large mirrors with good optics for good seeing power and sensitive electronics for the spectral/intensity measurements. Those two things weren't readily available until the past few decades...which surprise is when exoplanet discoveries started happening.

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.