Honestly, old school guys were more aggressive because stalling was much less a part of the meta game and culture than it is now. Not to mention they tended to have better takedowns, so there was very little stalling on the feet. What they didn't do was play as many lapel games, invert as much, or use as many leg entanglement type positions (50/50, SLX) as are used now. They weren't generally as competent of leg lockers as modern players, even under IBJJF rules. The passing and guard games were simpler and they had a stronger preference for closed guard. But they were also more submission focused and much less concerned with shutting down their opponents' games by reaching certain positions like 50/50 to win on points. I generally find old school matches more entertaining than modern ones for that reason.