Ofcourse…
Flexibility is, without any doubt, a very important ingredient for a successful marriage, but one must know from what starting point they are being flexible from.
I see so many young people getting married that clearly do not really know who and what THEY are, and/or want to be.
Then, a few years down the line, when they finally have started thinking about this question, and started formulating and crystalizing what their own hashkafos are, – about frumkeit, about politics, about career, about financial issues, about children, etc., etc., etc. – then they realize that their spouse is on a totally different page.
How much better off they would have been if someone would have advised them to do some hitbonenut, some serious introspection, about these issues BEFORE they sought out a mate.