Your question assumes that "the more inventions, the better for sociaty". While this may have been true for the last five hundred years, maybe it's time to reconsider the assumption?

This may sound foolish but please consider: What is more important? To create pills that enable old men to have sex or to solve today's energy problems? The later is not just about new technologies but to overcome the old established structures. Or consider medical treatment: Do we really new technology to heal very uncommon ills for a rich upper class when a large part of the sociaty cannot afford to have well-known basic medical treatment? The later is a social problem, not a technical one.

Another assumption of your question is that patents are the only way to secure a large investement and that there are no alternative barriers to entry for others. However, that is clearly wrong. Do you have the money to manufacture automobiles, for instance? Even if you're capable to invent a new kind of car, do you have the money to advertise it properly?

The third assumption of your question is that we may need a completely different system. However, patents seems to work somewhat fine for the material world. It just doesn't work for software. So, maybe we should not look for an alternative but for a different, a better kind of patent system?

I'm not saying I have an answer. I just think one should be careful about either/or questions.