There is no such thing as an unambiguously objective reality without a subjective consensus — which is an impossibility. From your vantage point as a co-creator of the collective human experience, and as the sole creator of your human experiential aspect, this must unambiguously be accepted as objectively true.
Consider for a moment the UFO hunter or the Flat-Earther, the atheist or the opposing party zealot. Each of these perspectives has created a reality in which alien intelligence, a flat Earth, an unknowing void and God’s politics exist. These realities exist within the experience of the believer — they may be malleable, but in the infinite now, are unarguable. They are real in that moment.
Hallucinations, chemical imbalances, ignorance, willful disregard? All merely ideas stacked upon ideas in order to perpetuate the realities of the skeptical ego.
How many skeptics or naysayers must be decidedly correct in order for these realities to collapse?
Every single one of them.
How many true-believers need to be right in order for any or all of them to be a reality?
One. Just one.
So, are aliens real? Yes and no, depending on your perspective. What reality are you creating? Is it expansive or contractive?