The phrase "are just a mere" is correct and usable in written English.
It can be used to emphasize that something is insignificant or trivial in comparison to something else.
Example: "These complaints are just a mere distraction from the real issues at hand."
Alternatives: "are simply" or "are only".
So here we are just a mere few hundred year into the new Anthropocene Epoch and we are already failing as a civilization because we simply have no leadership and willpower to cooperate with each other enough to protect our long term future and prevent our decline and fall due to our myopic brain defect.
From the 15th century to 2015, these are just a mere portion of the artists who've turned to art in the face of loss.
Of course those are just a mere two, among countless, similar violations of the Uniform Code of Military Justice in the fraudulent name of "religious freedom".
In the middle of 2012 there were just a mere 1.55 unemployed for each vacancy; a year ago this had risen to 2.5; now there are on average 3.55 unemployed fighting over each vacancy in the state.
I was just a mere student, you know, just finished secondary school — and this is my aunt, this is my uncle.
It's so easy to say, "Yes, I accept your apology," but that could be just a mere step away from saying, "Yes, I accept you".
But she enjoys the pace of the restaurant and is grateful for an experience that's different from when she was just a mere summer vacationer.
Therefore, it is confirmed that the role of the market cannot be just a mere impersonal mediation.
Either no (non-vacant) championships are changing hands as this is just a mere exhibition, or WWE is saving all the heat for Roman Reigns' moment.
In 2005 it may seem like an old story, but let's pause to remember that as a commercial product the World Wide Web is just a mere decade old.
Time is just a mere excuse and a place to put my blame and anger towards.
