Look I don't own an espresso machine nor do I work as a barista so I haven't read a single word on espresso science but from things people have said on here and youtube I think espressos are intrinsically more sour than other brew methods,

logically what I can deduce from that is that espresso extraction profile leans more on the sour/juicy side, probably it has to do with how different substances extract,

I haven't tried many craft coffee espressos so I can't really say but I think you can manipulate the extraction to shift to a less sour profile if you desire but I think that if you don't like the sourness you should switch coffees, some coffees are suposed to be pleasantly but intensely sour and espresso can accentuate that,
I distinctly remember The Coffee Chronicler in his video on robusta coffee pulling an espresso from 100% robusta and saying he prefers it to a lot of arabicas since they are too sour for him in espresso form,

Now OP doesn't seem to understand how physics work so (saying this with no real proof, but even so...) they could also have no idea how to dial in an espresso properly, since they are using a plastic manual espresso press there's any number of things that could be happening, namely water not being hot enough for light roast or pressing too fast to try and achieve the 9 bars they think are elusive because of their weight,

If they also do the same on a coffee machine it could just mean they don't know how to dial in properly so instead of changing the grind size and water ratio they go for less pressure (I don't know if you can manipulate pressure on an espresso machine at all so I'm just talking out of my ass here)

Hope this made things clear enough to be cofortable in the unknowing at least