I'm trying to say people must be more wary in a society more and more false. That is more people and things are not what they say they are - or appear to be.
The sentence is:
... more important to be wary in an increasingly ___ society.
Personally I am a cynic so I would say
more important to be wary in an increasingly deceitful society
But for me any of the following would work; treacherous; perfidious; deceitful. Perhaps "perfidious" is the most accurate
Ostensible or specious seem a bit vague, but that's my opinion, superficial sounds the best of the three. However it's your sentence you know what you want to say.
deceit noun Cambridge English Dictionary (an act of) keeping the truth hidden, especially to get an advantage:
The story is about theft, fraud, and deceit on an incredible scale.
When the newspapers published the full story, all his earlier deceits were revealed.
perfidious adjective, literary unable to be trusted, or showing no loyalty:
She described the new criminal bill as a perfidious attack on democracy.