The way that I am interpreting this is that if I were to invest in one of these (i.e. Maker) then the returns that I would see are there purely because other people are investing in it.
That is close to what most stocks do, but at least with stocks in a company the value is not driven by the mechanism by which it is traded alone, but also by the decisions and profitability that the stocks are backing.
That's the opposite of what I'm saying. The returns are from other people using the platform, not from investors in it. For Maker, using the platform means borrowing. For Uniswap, the returns are from a small % fee on trades. It's exactly analogous to a traditional company.
This is essentially the "problem" at heart of all crypto "currencies". There is no real world use case that imparts human value, apart from its utility as a speculative vehicle to grow wealth.
Every new DeFi application is a new layer to lock in current adapters who would've otherwise already cashed out. Crypto as a currency is a concept dead in the water because of the perverse incentives of finding every corner of arbitrage between non distinguishable (and frankly worthless) alt tokens/coins.
The entire world of crypto is nothing else but an experiment of how much one could financialize a fully non-regulated, intangible, and imaginary "good" based on nothing but greed.
If it was a ponzi scheme they would be spending millions on advertising and use fear of missing out to get more people to invest.
Wait....