if blocks are taking much longer than 10 minutes to be found and the mempool is growing drastically.
That is not bitcoin's design.
Bitcoin's design is to, over a long period of time, have the average ~10 minutes per block. A block taking an hour can be a daily occurrence. You can't say a system has failed to perform when it performs as it was designed. You can say the design is a failure, but that's a different argument.