I have visited this site many times as I used to live in the area and I found the above review to be rather superficial if not a bit uninformed. For starters there are many other buildings that make up Independence Historical Park scattered over several blocks including the First and Second Banks of the United States, the Mercantile Exchange and the Tomb of the Unknown Soldier of the Revolutionary War that are given short shrift in the review.
To say the site is surrounded by "blinking skyscrapers" does not do justice to its history. Before the park was created in the 1940-50's the historic buildings were completely surrounded by the modern city and some were still in use by the city government of Philadelphia. After the US government took over management of the park an entire block of 19th-century buildings was demolished (not without controversy) to create an open vista (Independence Mall), buildings were restored to their 18th-C. appearance and a wave of gentrification swept over the neighborhood so that what was once a blighted downtown area became a cohesive 18th-C. Old Town along the European model. The adjacent neighborhoods of Society Hill and Washington Square contain many beautiful streets filled with 18th and 19th-century houses, churches and other buildings not officially part of the park but which add much to the overall ambiance.(Carpenter's Hall, Newmarket stalls, Quincy St., Delancey St., Christ Church Burial Ground, Philosophical Hall, St. Peter's Church, the Quaker Meeting House to name a few). This project spurred the reclamation and restoration of Colonial and Revolutionary War era buildings all across the United States and is really a triumph of historic preservation over neglect. In that way I think this site perfectly embodies the spirit of the UNESCO list.
Independence Hall and the other buildings in Independence Sq. are lovely examples of English colonial architecture. The fact that they are made of brick and "tiny" seems beside the point. The buildings were built for the colonial government of Pennsylvania and the city government of Philadelphia in the then-current Georgian style. The Federal government only occupied the buildings temporarily while the new capital was being built. They are not really the products of a national government, but of a small but thriving English provincial city.
I have known several Europeans who found Philadelphia to be charming. A few even pronounced it "very European" (apparently the highest compliment they can give.) Frankly I think a visit to Independence Historical Park more worthwhile than is credited in the review. Perhaps one only gets out of a visit to a site what one is willing to put into it.