No, I'm actually German 
Funny story about me owning an MG, yeah... the F is a nice litte car though. Loads of fun to drive, and quite affordable these days. A lot of bang for your buck.
Anyway, looking at the GIF library, it kind of looks like it's so bulky because it tries to cover every possible case of what kind of data might be inside a GIF file. I am thinking if I keep the parameters of my own created GIF files within certain boundaries, I might not need much code in the first place. I also wouldn't need many of the if statements and error messages it can print out if certain criteria aren't met. I could make sure they are met in creating the files to begin with. So I could boil things down in that respect.
Also, this library only seems to accept files loaded from an SD card. Especially on the ESP32 with 16 MB of flash, I would like my images to all be in PROGMEM.
In terms of leanness, I would like a GIF decoding function to be more along the lines of the showBMP() function in the showBMP_kbv_Uno sketch. Using the LZW algorithm probably means significantly more code still than in showBMP(), I know.
Maybe I will be able to extract the actual LZW algorithm from that library and use it for my purposes. I'll probably have a closer look this weekend.