Is this a skill issue if you don't understand things without subtitles?

The majority of what you listen to (mostly blackboxes and recordings) is just so smudgy it doesn't make any sense to me. There are only some words that you occasionally pick up on but almost never the full sentences

The exception being the main story line which is dialogues between Simon and Catherine. Those are 99% clear

P.S.: Do not suggest turning the subtitles on. I finished SOMA quite a while ago and now I've decided to play it again with more immersion (and it actually works for the most part). Also I'm not a native English speaker but I don't think it plays THAT huge of a role

Is this just me or has anyone else experienced that before?