It's not a lot. Here are the interesting things:

The more you learn about them the more they lose their interest. Dai and Compound in particular are forms of lending eth programmatically in order to accrue yield. If you put some of your eth in compound or in a dai vault, you can borrow or issue stablecoins against it. This is only useful for those who want to go short on eth (any stablecoin is inherently identical to a 1x short position) or for those who want to go long on eth (by selling the stablecoins for more eth and then hoping to pay back the loan after the price of eth rises). That is gambling and yield chasing. It is not a sign of a "vibrant economy" but of a very sick one full of degenerate gamblers who expect to gain money without work. Uniswap's sole purpose is also gambling. You can swap the token you think will go down in price for the token you think will go up in price. That's it.

Rollups are the only one of those that actually has any compelling long term interest because it is a useful way to scale up the number of payments a blockchain can process. They are roughly equivalent to what we bitcoiners call drivechains. Maybe someday we'll have them too.