The fallacy of “slippery slope” means assuming that one thing will lead to another without evidence this is necessarily the case, and perhaps even contrary evidence that it will. For example, many people in communities based around isolation have the idea of certain milestones that confirm an identity. This can sometimes be quite formalised. I don’t remember which country now, but I met a north European once who told me in his country that if you aren’t married by the time you are thirty you get some gift, I don’t recall if it’s a spoon or an egg timer or something, and they call you a wizard (this is for men). I think this is meant to be light-hearted but people do internalize these identities.
SAND HAS NO LINES
You might see on a forum someone in their late twenties saying they’re worried they need to find their first relationship before thirty. If you stop and think about it (which is what I am hoping that people will do) then there is no reason a person couldn’t find their first relationship after thirty, there is no definite line in the sand. You could possibly say that it will be harder. You could possibly conduct some study and it is less likely, but you could also go out and find examples of people who wanted and achieved this.
Also, if you think it through logically (reason it, in other words), then there would also be advantages to trying to find someone as an older person. The other older people you are looking for are also in a reduced dating pool (more partners married off), they are more mature and reasonable, more likely to want to find a long-term relationship, so perhaps the issue is then looking in the wrong place. Where would these people be? So now the direction of thinking changes.