It's been a while since I worked with FPGAs but my experience was that using drop-in CPU cores and peripherals is pure joy, drag and drop what you need, build y

It's been a while since I worked with FPGAs but my experience was that using drop-in CPU cores and peripherals is pure joy, drag and drop what you need, build your bits and you're good to go. Replacing an I2C with SPI or supporting a wide range of daughterboards is trivially easy. On the other hand, it only takes a day of writing low-level Verilog to realize that the problem of correctly and efficiently parallelizing algorithms is a hard one. We were using a very early C to Verilog (C2H) compiler from Altera and it worked but was very inefficient in terms of logic element use. I'm sure there's a lot of R&D going on in that space because without significant progress general purpose CPUs or at least cores will remain dominant for some time.