As mentioned, I'm following the Copernican principle for this line of questioning. Yes I've considered and read many other possibilities, but this question is for Copernican-style answers ONLY. Your welcome to ask your own similar non-Copernican question in a separate question, and inform me and I'll give my support as well as my own best answer(s), or you can ask me to formulate my own non-Copernican version.
Estimations are based on various websites, feel free to adjust inaccurate numbers if they change a final formula by more than 5%.
Also, please no government-conspiracy type responses.
Summary: why considering these and other numbers, haven't we already found mainstream accepted proof of an ETI?
The numbers: quick search indicates that within 50 Light years (I'll abbreviate LR) of us, 133 stars are visible to the naked Eye, and 1400 stars are found and/or estimated to be in that 50 LR span. As I understand it (introduce some shaky logic with semi-arbitrary numbers and conjectures), we've been sending highly "unnatural" signals to space for about 50 years. Many of them I assume probably aren't strong enough to be detectable past a LR or two (pure conjecture) of space with our own detection instruments, but some I assume probably were strong enough to make it through the noise. I think perhaps our nuclear detonation may also have been able to be detectable by even an earth like civilization.
Also read that nearly all of them have (or probably have planets). And 25% have or probably have planets in the habitable zone.
That's 350 in the habitable zone within 50 LR of us. If 1% have life, that's 3.5 If 1% with life have intelligent life, that's .035... so maybe 1. The number of planets our signals will reach grows exponentially as time goes on. I'll arbitrarily say that in another 100 years we're at something like 160,000 stars reached, 40,000 have planets with life friendly conditions (assuming 25%) thus 400 with life (assuming 1%), thus 4 with intelligent civilizations (assuming 1%, which I will point out that if we applied the copernican principle to this portion of the formula this makes us "special" but I'll make an exception here) Recap: 160,000 stars in 150 years.
Us plus the other intelligent civilizations at a 25%/1%/1% formula makes 5 intelligent civilizations for every 160,000 stars...
Now the copernican principle.... if you took it very seriously, and if my math is kind-of accurate, then we should have inadvertently been sending unnatural signals, with various levels of detectability through space for 50 years. If we "imagine" that we are just an average form of life, and that the universe may be teeming with life (since here we are assuming we're not special, wether it's lone survivor, or short-bus special) then also if we are not special, the universe should be teeming with life; and surely a bunch of it would also use signals similar to ours, maybe not decipherable, but at least similar enough to differentiate between natural and unnatural. Yet per-Fermi's paradox, they have not been detected....
The question: why the **** aren't we noticeably detecting their signatures if we ourselves have been able to send stuff through space for 50 odd years???
Looking for fresh ideas. If you HAVE to, you can point out the great filter or some other already mainstream hypothesis. I'm not discrediting them. Yes many of those types of ideas have merit Imho.
Looking for fresh thoughts and discussion on this, while preferably being able to hold true to the Copernican principle. Again, I'm not saying they're like us because we're awesome, I'm saying if they're there, then too assume WE are like THEM since we may NOT be awesome nor behind the curve, nor on a separate playing field, just average.
Last words: I'm not saying we're not special. Yep, we might be. We might be the only ones or the only ones to make it through a filter(s). What are some other "non-special" possibilities, that might allow ETs and ETIs to exist, while keeping us from seeing them, and perhaps keeping them from seeing us, or each other as well