FPGA speed is a common misconception. They often have run at quite modest frequencies, and come with limited memory capacity compared to a GPU at same price range.
Speed (clocks speed) , is dependent on your design layout, and for any resonably advanced layout, it takes lots of knowledge to push the clockspeed beyond 200Mhz on 'consumer'/prosumer models. (Compare to a few GHz for GPU/CPU).
FPGA speed shine where they can pipeline massively parallel calculations through pipelines with minimal lookups.
>with minimal lookups.
Wrong. This is one area where FPGAs have an insanely unfair advantage compared to CPUs and GPUs. Yes the SRAM is limited but you have so many individual blocks and all of them come with dual ports and getting the maximum frequency out of block RAM is much easier than getting the maximum frequency out of programmable logic.
If you wanted the highest possible memory bandwidth while being free to look up hundreds or thousands of independent memory addresses at the same time you're better off with an FPGA.
E.g. with an Efinix Titanium Ti180 you could hypothetically have 2560 simultaneous memory requests per cycle all pointing at a different address and process those requests at 1 Ghz.
You can get 900 MHz designs on FPGAs, but yes you need very good engineers and patience to get that.
Yes SRAM is limited but that's more of a ram-process limitation than a limitation of FPGA