I think you may be exaggerating the necessity of solitude.
There are many aspects of prayer. Corporate prayer, which is obviously not solitude, is essential to our faith -- we have an obligation to attend liturgy every week, and daily prayer is encouraged as well.
Married couples can and should pray together. There is nothing wrong with group prayer at all, after all Jesus said, wherever two or more are gathered, I am there in their midst. (Matthew 18:19-20) However, because ultimately no one else is responsible for your relationship with God but you, it is also essential to establish a one-on-one relationship with God, and that is done by one-on-one prayer.
It's like a marriage: There are two of you, and you need to spend time with each other apart from anyone else to cultivate that relationship. I'm not convinced this needs to be solitude per se, as in being isolated and alone. One can pray one-on-one with God in the same house as one's spouse, perhaps even in the same room. The conversation just needs to be one-on-one, not the presence.
Only hermits live in radical solitude and there aren't many of those.