Uniswap works. Just the fees are too high.

Uniswap governance just voted ~two weeks ago to deploy UniswapV3 to Polygon . I've never paid more than a penny for any Polygon fees so hopefully this along with wrapped version of coins will reduce my need for Ethereum. Other DeFi exchanges such as SushiSwap have already gone multi-chain to multiple chains as well. Mark Cuban recent talked about the BCT (Base Carbon Tonne) token which unless you mint yourself (via staking a real carbon credit in the real world) you must get via SushiSwap on Polygon at this time - I think he just invested another 50k into it

I will say one thing about Mark Cuban - he's deep into the DeFi/dApp world and seems to actually know his stuff on a deep level.

NO. Uniswap does not work. There are too much details but. In short it just works when there isn't volatility and there aren't many people trading so their trades doesn't invalidate each others trades because of high slippage which has to be set low because otherwise arbitrage bots exploits slippage tolerance.

I've been curious about decentralized exchanges. When you say they have a bad track record, can you share some examples? Uniswap is the one I know of, as far as I know it has a fine track record.

Check out rekt.news if you want a long list of defi hacks, including many decentralized exchanges.

Of course, the code running a DEX is fully auditable by anyone, unlike the code powering a centralized exchange.