I have come to believe strongly that those who simply MUST have miracles to believe will find them - but that what they find might or might not be of God, and what they find might or might not be good for them even if from God.
I have experienced the truly miraculous a handful of times, and at least one of the times I was exposed to the miraculous was a horrible experience with someone whom I believe truly had connected into an evil that I simply can't describe adequately - nor do I want to do so. Even typing about it brings back memories I don't want in my mind. However, I also have known good people who have experienced the miraculous and then obsessed over it to the point that they became miracle junkies - desperate for the next fix and convinced that their experiences made them special in some way, causing all kinds of damage to themselves and their families and acquaintances.
Finally, I think we tend to interpret the statement about an evil and adulterous generation seeking after a sign too narrowly. "Adulterous" is most commonly aligned with sexual sin, but one of the definitions of "adulterous" is "illicit" - and that word means "not legally permitted or authorized; unlicensed; unlawful; disapproved of or not permitted for moral or ethical reasons". In this light, and the overall context of the original statement itself, it is clear to me that the description is one of someone who "cheats on" God - who is UNFAITHFUL to the covenant he made with God.
The core of that covenant is faith, which, at its center, means an allowance that there are some things that are unknowable - that "signs" (proof) are not required for belief and discipleship. Demanding signs and miracles, therefore, is a direct repudiation of faith - since it takes the decision of when and how to present the miraculous to individuals out of God's hands and demands this be done according to the desires of the mortals who are unwilling to wait (to "be still, and know that I am God"). Again, I believe in the miraculous, and I have experienced undeniable miracles a few times in my life, but none of them have come through me seeking them.
Sometimes, stillness is essential - and seeking for signs makes stillness and patient, humble reliance and faith impossible.