Jfem, you are assuming that on a large scale, men and women who are dating are not displaying their true personalities, and this is causing then not to marry.
I think you’re misinformed in both counts.
Most young men and women who don’t socialize outside of shidduchim get over their awkwardness after a couple of dates. A good shadchan will usually be able to prevent any initial awkwardness from derailing a good potential shidduch.
Also, within a year or two of beginning the shidduch process, the vast majority of singles (especially boys) are married, certainly, it seems, at a much higher rate than those who do socialize outside of shidduchim.