Uniswap v4 feels like crypto's first complete product. Uniswap v3 was already nearly there, which is one reason why while previous versions took ~1 year, v4 took 4 years. I can see additional functionality (e.g. unified liquidity) and responding to infra changes (e.g. quantum-resistant zkVMs) that will justify a v5, but the core purpose of this application now feels complete for the foreseeable future. What's remaining is now on the governance & social end. 

Aave v4 is the next candidate for a complete product. Interestingly, the applications are hitting final form years ahead of the infra they're built on, and in cases like Aave v4, being intertwined with infra itself.

(Side-note: of course, simple "products" like memecoins or USDT are "complete")