Similar to ASIC's, the problem with FPGA's is they are of limited use on memory hard algorithm's. I remember back in 2018 there was talk on developing FPGA's for accelerating GPU mining, but I don't think they have produced a working unit as of yet.
https://bitcointalk.org/index.php?topic=4391318.0Yea big failure with Squirrel, I was waiting for that and glad that I didn't purchase.
Hashaltcoin seems to be good for FPGA miners but with shit coins. I can see what you mean with the memory because of some coins that are little more famous but can do much.