I think people are confusing infertility with sterility. To address this, let’s start with some definitions:
If you are infertile, you are unable to conceive within a year of unprotected intercourse.
If you are sterile, you are unable to conceive naturally.
To oversimplify: Infertility is reversible; sterility is not.
One study estimated that sterility occurred in ~1% of the population. Sterility status does not change with age. Unfortunately, if you are sterile, there is not much you can do about it (other than explore alternative reproductive techniques or adoption).
In that same study, infertility was estimated at 8% for women aged 19-26 years, 13-14% for women aged 27-34 years and 18% for women aged 35-39 years. Infertility rates rise with age, mostly correlated with egg quality and overall health. Because we can improve egg quality and overall health, we can also improve fertility.
This study concluded as follows: Increased infertility in older couples is attributable primarily to declines in fertility rates rather than to absolute sterility. Many infertile couples will conceive if they try for an additional year.
The point here is that only a very, very, very small percentage of the population cannot conceive naturally...far fewer than we’ve been lead to believe.
Yes, it is true that older couples may take longer to conceive than younger couples. Yes, it is true that older couples may also be having sex less frequently than younger couples. Yes, it is true that older couples may be less healthy than younger couples and that may complicate their pregnancy attempts. There are many factors at play here.
So, instead of the mantra “keep doing what you’re doing...just do it longer”, I would suggest otherwise. Yes, there is an element of patience required in getting pregnant. You can view it as your first lesson in parenting! However, there are plenty of things that you can do today to improve your chances of conceiving and carrying a healthy baby to term, regardless of your age. Start there and see if we can't accelerate that timeline just a bit.