Here is my opinion on this
The LSPDFR community are lucky,that we have these talented creators making content for us. Everyone of them spent a lot of time making their content and some even spend money on various stuff,and then release their content on here for free. Yes...A lot of the cars are upscaled and can't be used by people with low tier computers.Is that a dev problem? Absolutely not.
If you know your computer is not that good,then chances you shouldn't being modding the game in the first place.As most mods on any game,will require a decent computer to run the mods at a decent FPS. Most devs even mention this in their "Read Me" files.If you have a problem with that,then there are several simple solutions to this problem.
1.Just don't download the content.Can't harm your game if it's never installed.
2.Learn how to make the content yourself and make it to your specifications.
3.Request customs vehicles from devs and pay for them.
4.Just save up and upgrade your computer.