The response is that Uniswap is a set of Smart Contracts that run on the Ethereum blockchain and, as such, needs gas to perform some functions.
That is, when you swap token A for token B or token C, the same feature is named in order to execute the required logic of matching buyers and sellers.
This is just a problem when gas prices are high or the valuation of Ethereum is high (for example, a $50 charge to do a $10 trade) (both of which are true right now). As a result, many consumers reduce the amount of petrol they are willing to spend in order to make the purchase expense manageable.
Others have raised the price of gasoline in order to make their transactions run more smoothly or quickly.
As a consequence of these conditions, we have a large number of canceled transactions as well as a large pool of unseen or unconfirmed transactions that are waiting to be propagated across the Ethereum network by miners.