The difficulty with a siege in higher tech settings is that once you have reliable long-range explosive weapons (artillery and bombs, basically), the besieging troops become sitting ducks. And on the other hand, if the attackers have good long-range explosive weapons, they can knock a hole in any reasonable thickness of walls in a few hours. One way or another, what would have been a months-long siege using medieval tech becomes a quick and decisive engagement, in one direction or the other.
It should be noted that long sieges were never common. Both sides could do math -- basically, how long could the attacking force stay in the field (farmers had to get home in time to harvest the crops, for example). versus how long the fortified location could hold out based on its stored food and access to fresh water, combined with the odds and timing of the arrival of a relief force. If the math favored the defenders, the attackers never started a siege. If it favored the attackers, they typically surrendered quickly to get good terms and avoid senseless bloodshed and property damage. If an active siege did start, everybody re-did that math in real time and changed plans accordingly. A defending force that "should" surrender and didn't do so could expect to be treated very badly when the attackers finally got in. Shakespeare portrays this beautifully in "Henry V" at the siege of Harfleur.
The whole trend of military history over the past 700 years or so has been to put a greater emphasis on maneuver. On a modern battlefield with roughly equally well-equipped forces, to sit still for long is to be dead. Just for example, while Iraq was likely doomed no matter what in the first Gulf war, they made things much easier for the US by digging their tanks into prepared defensive positions that prevented the tanks from maneuvering. It amounted to a shooting gallery for US antitank weapons.