I know many instructors at NY community colleges. I know some who are adjuncts at a 4 year university and at a local CC. In NY, the community college classes are taught at a much lower level than at the university. The students who start at the cc are often (but not always) less well prepared for higher level classes than those who started at the university. That does not mean they can’t succeed but they often fail to produce the level of scholarship that those who began at the university are capable of. In terms of the foundation courses, they are markedly different and much easier at the cc. Students who would not pass the foundation courses at the 4 year school may get As at the community college.
The reality is that for some majors, the foundation courses are more difficult than the upper level classes. The early classes are often survey classes that move rapidly and cover a huge amount of material. They are required and don’t allow the student the luxury of focusing on topics of interest. In contrast, the higher level classes often cover less material (although presumably have more depth), involve more discussion and allow more selection of areas of interest. They require less in terms of acquiring huge amounts of facts/material. Students who took foundation classes in less rigorous schools won’t necessarily do poorly in upper level classes. They will just never know a large amount of more general information that will be known by those students who got a strong foundation in a rigorous school.
An analogy: consider someone who studies cartography. Usually the student would learn the layout of the world, the country, etc and then may specialize in maps of a small area, say New Orleans. Studying the layout of the world would require memorizing a huge amount of information, much of which might be boring to someone interested in a very specific area of the world. In contrast, learning the details about New Orleans would be relatively easy to someone whose interest focuses on that city. It is obviously possible to simply jump to the study of New Orleans without knowing much about the layout of the world, state, etc. You could probably get 100s on a course that focuses on the layout of New Orleans without ever knowing what country New Orleans is in. Would you be the same as someone who had a good foundation? No.