Several points, then an answer.
One. Yesterday was not "arguably the most boring semifinal in world cup history". come on. The world cup's been happening for 70+ years. The teams were tactically sound and there was a lot of good football. Not crazy exciting, but 0-0 doesn't automatically make a game boring.
The notion of a game being allowed to extend beyond 120' is silly because even after 105 minutes the players start to fatigue so much that the quality of the game decreases drastically. Yes, it could force a team's hand and the "strongest" may win, but they would be winning by their stamina not their soccer prowess.
Elimination of the offsides rule would increase scoring. Defenders would sit deeper, but that would not compensate for the volume of unanswered chances taht currently occur but are voided because of offsides. it would dramatically change the dynamic of the game, however, and reduce the quality becasue it would be more burte force and cherry picking and less creativity to penetrate the back line.