It's no secret to even the casual observer that relationships in our times are fraught with challenges. Marriages used to carry a greater expectation of stability. The stability of today's marriages seem to require more prayer and work.
There are many reasons offered for this change. To mention several of them in passing, they include greater sexual permissiveness, expectations of instant gratification, greater cultural mixing, new sets of pressures, social media, etc.
Truthfully, since the Creator is Good of good the core reason for any development is always gleamingly positive. Reasons of any other kind are, at best, external symptoms and not the inner core of truth.
So this development too needs to be gleamingly positive at it's core. Throughout history the Creator is preparing humanity for the arrival of the Messiah. The messianic era is a period of tremendous enlightenment. The prophetic verses describing this era speak of a time when the world will be filled with the spirit of God as the waters cover the sea bed or a time when the spirit of God will be poured out on all flesh. Jewish tradition also describes a whole new level of Torah which the Messiah will reveal; one expected to explain reality in a whole new way.
So commensurate with this upcoming enlightenment, people's minds and hearts need to become broader and more expansive. To accomplish this goal, cultures are mixing and a constant fresh influx of knowledge and awareness has become the new norm.
Even people who ostensibly belong to the same community and cultural group are finding that their minds are being moved to very different directions as a result of what they are exposed to and how their minds process new exposures. People are all over growing in different ways, rates and paces. As people's minds become more different, so too they become more different as well.
(Though the cosmic goal is to eventually lead all minds to the same expansive place, in the meanwhile the groping and growth required to get there creates a temporary state of global mind differentiation. It's a temporary differentiation for the sake of a much more expansive similarity. Think about how fetal cells differentiate in order to form a much larger unified body.)
Maybe, this differentiation isn't to the extent of making friendships difficult, but because marriage is much more sensitive than friendship, it does seem to make the real close quarter intimacy of marriage more difficult.
A solution might be to try to find a partner as similar as possible. However, also realize what is happening. "Similar" is a relative term, a spectrum. So it's not as likely that one can expect the similarity of yesteryear's more homogeneous societies.
Therefore, one should regard one's intimate partner as an opportunity to grow in perspective; as each partner brings something different and beautiful to the table. Bridge that gap! As a couple's minds blend, so will their identities.