If the design is amateurish, that's one thing but...
plagiarized or copy paste
from other website are usually consider to be stolen content. Hence it destroy the gravity of the project totally.
Even though it could be consider as lack of resources to fund the project.
Plagiarizing is never okay and deserves to be punished. Saying it's justified because of lack of resources is akin to saying that robbery is justified if the robbers are poor. If they can steal content, they can steal users' funds, so saying that it's a scam is completely justified. If teams don't have the funds to even start a project properly, then maybe they shouldn't start one at all. If they couldn't even be bothered to invest in their own project, why should others? Not saying that insufficient funding = scam project, but how much the team is invested in their project reflects on their commitment to it, which could also explain why scam projects are typically underfunded.
Anyway, I don't think anyone will accuse projects of being a scam just because the website is poorly designed for as long as there aren't obvious red flags like plagiarism, lies, etc. Either way, scam accusations aren't a one-way street; you're free to prove accusations against you wrong.