Poor encoder: FAAC/FAAC2, the first open-source encoder for AAC audio, produce terrible audio no matter how much bitrate you let it work with. The AAC standard itself facilitates crisp audio quality at low bitrates, as heard with e.g. Apple's Core Audio AAC encoder or Nero AAC.
Poor encoder: Xing, a popular MP3 encoder of the early 2000s, was similarly infamous for producing chirpy and slurry audio even at or above 192 kbps, while bona fide MP3 encoders like LAME do far better on less.
Poor encoder: NVENC, Nvidia's on-GPU hardware video encoder, produce very poor H.264 video even at 8-10 mbps, even on the current 8th and 9th generation (RTX 40/50 series). Good H.264 encoders like x264 is capable of producing excellent FullHD video at just 2-3 mbps.
Poor standard: Vorbis is a good example of a spec whose limits/mistakes make it impossible to preserve certain combinations of frequencies, resulting in brief passages where parts of the reproduced spectrum deflates, making some music sound as if it lost its breath, so to speak. When fed certain "triggering" audio content designed to expose problems in the spec, Xiph's reference Vorbis encoder will produce ringing sounds. Interestingly also the MP3 spec has similar limitations where certain frequency combinations (usually towards the lower and upper ends) will reproduce with quantized amplitude, even when encoded with LAME, though the outcome is nowhere near as pronounced as it can be with Vorbis.
Poor standard: MPEG-4 ASP, being limited to 4:2:0 chroma subsampling and PAL/NTSC resolutions. My beef with 4:2:0 is because of how harsh it is on low-resolution content. MPEG-4 ASP being limited to a maximum of 720x576, and the 4:2:0 chroma coverage being only a quarter of that, is the reason why DivX/XviD content is smudgy even with reproduction filters.
On FullHD content a 4:2:0 grid has almost three times higher resolution, which I agree works out on both still scenes and slow panning (the two scenarios where low chroma resolution makes itself most reminded).