Q. I’ve been told that single people’s mitzvos don’t count. Any validity?

A. They definitely count. There are very few mitzvos and traditions that a single individual after bar mitzvah does not have to observe and fulfil. Some of them are; 1) wearing a Talis Godol when praying in many Ashkenasi congregations or according to some opinions, 2) not performing birkas cohanim (Shibolei Haleket 23 ) since an unmarried person is not considered as being truly content (Yevomos 62b,) 3) being the choicest individual for leading services and blowing shofar on Yamim Noraim, 4) If he is a cohen not sacrificing a korban in the Beis Hamikdash (Zohar – Vayikra p. 5, Naso 145,) and a few more.
However, definitely the importance, quality and excellence of the Torah learned and mitzvos performed when done with kedusha and holiness, is boundless. As our sages teach; The one living without a wife is living without Torah.(ibid.)
Horav Shlomo Mille’rs Shlit”a opinion is similar.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a