The Reapers have been around for over a billion years. That's billion with a B. This is before dinosaurs. Before anyhting more advanced than algae existed on Earth. They were harvesting organics back then.
It doesn't matter if the Reapers are the pinnacle of technological advancement. The idea of surpassing them in anything significant in a time period of something so tiny as a human lifetime, or even several of them, is pretty laughable, If there was such a simple method, the Reapers would have found it long, long ago/
The reapers aren't a self-advancing civilization making progress to advance their culture, make new medicines, forms of entertainment and adapting new technologies.
They are the result of an artificial intelligence using the technology of its time to preserve organics by harvesting them, salvation through destruction as it were, and they have become very efficient at it, but at their core they are still following their programs, and have left the mass relays so new civilizations will develop on the technological paths they require before they harvest.
From what I can gather, this cycle was meant to be harvested before humans made it to the galactic stage, probably back when the Geth first revolted against the Quarians, or maybe even during the Rachni wars if the Queen is telling the truth in ME2 about them being forced to war, but the actions of the prothean survivors on Ilos kept them from pouring in from Dark Space.
They aren't the pinnacle of technology. They are the pinnacle they would allow following a very specific tech tree, as it were, and they usually strike when artificial intelligence is coming around and not long after they do and develop on their own like the Geth.
The cycle during Shepard's time is full of anomalies the Reapers haven't dealt with yet, at least to our knowledge.
And even then, it won't that big a deal because there already is an in-game example of new mass relays being built and not by Reapers, and that's the conduit built by the protheans as a prototype backdoor into the Citadel.
But the idea of the Reapers being the pinnacle of technology implies that there is nothing bigger beyond even them. And given enough time and resources, there may very well be, especially if there is no Reaper intervention harvesting life just as they start developing AI.