The problem with this thinking is that it conflates all technology with those technologies that are integral to war, when in reality there has been lots of technology whose utility for warmaking has been rather limited (or at least, whose utility for war came secondary to it's civilian utility). The wars of the 20th century have seen all sorts of great advances in technology; jet engines, submarines, missiles, etc. But these are refinements on existing technologies that didn't need war to happen. Airplanes were a civilian invention. Submarines are really just an evolution of all iron hull watertight ships, a civilian invention. Missiles were just an evolution primarily of chemical technology. Hell, the use of explosives in militaries stems from civilian technology. Necessity certainly is the mother of invention, and while war creates a great need for advancement, efficiency does too, and over a much longer time span. War can focus the needs and resources to adapt technology to certain outcomes, but very few technologies were outright invented solely for military purposes.

I'd say it has largely changed in the past decade or two. A lot of the big tech advances these days, at least the ones that get sexy IPOs and press coverage, are tied back to the Internet and computing. Both of which are at least partly a result of defense spending.

Well I can think of a few examples that directly contradict the theory.

The industrial revolution had very little to do with military, let alone wars. The first steam machines where built to help in mines and factories ( source: "Iron, Steam, Money", Osbridge), and you would first have to prove any direct ( and even indirect ) links to say it was "because of wars"

And even before steam engines, in the Middle ages and the Renaissance the development of machines, gears, and e.g. clocking mechanisms was driven by making labor-saving, cost-effective ways of production, not for war. Agriculture with mills and windmills, textile industry with complex machinery for weaving, then clocks, books, nothing is directly war caused. My personal opinion is that even the improved navigation and shipbuilding techniques is more due to the desire to improve trade efficiency then to improve war making. ("Cathedral, Forge, Waterwheel" F & J Gies)

Not saying you can remove war completely out of the picture, as it always is interconnected and sooner or later new technologies get their war usage, but saying it was "because of war", seems exaggeration. I would be more broad: technologies advancement happen where they are funded and invested in both financially and in terms of man hours of capable people. War being a very good cause to devote money, time and determination into development of technology. But not an exclusive one, nor in my opinion historically the main one.

One important thing to note, is that wars actively destroy value by killing people, destroying infrastructure, and eliminating resources. Therefore, as the process of war grinds on, there is less and less resources and people to do things, thus stunting innovation.

In addition, the obsession with heavy industry that is so useful during war, is counterproductive and distracts from consumer goods that directly benefit individuals.