In Philadelphia, my guess is the Orthodox and Oriental church scene is bigger and more visible than in most of the rest of the United States but smaller and thinner than in much of the rest of Pennsylvania (a hub of Slavic Eastern Christianity in America, as seen in the movie
The Deer Hunter). All of the main players (the Orthodox big three in America: Greek, OCA, and Antiochian) are here as well as smaller ones: Greek (cathedral and several parishes), OCA (ditto), Antiochian (two parishes I know of; one Arab, one convert), MP (two city parishes, one, the pro-cathedral, vibrantly immigrant Russian), ROCOR (one parish; WWII exiles and some post-Soviet immigration), ACROD (two parishes, one a 1930s split from a Catholic parish), Ukrainians (two parishes), Serbs (one parish, moved from city to 'burbs), Romanians (one city parish; immigrant), Armenians (two parishes), Copts (at least one parish), and Malankara (one parish). The Greeks, OCA, and MP have cathedrals here; I think the latter are pro-cathedrals (no resident bishop). The nearest parish to me is immigrant Greek, followed by immigrant Arab Antiochian and a Malankara parish. Churches I've been to: Greek (twice), OCA (many times), ROCOR (ditto), MP (ditto), ACROD (three times), Ukrainian (once), and Armenian (once). Immigration replenishes several of these parishes. I can think of one convert parish, in the 'burbs; Antiochian. The city parishes not being fed by immigration are stolidly declining, in neighborhoods now moribund (the white ethnic parishioners have died or moved; the Ukrainian and Ruthenian Catholics are experiencing this loss too). Some pan-Orthodox stuff; mostly ethnic enclaves little to do with each other.
This has been something I had observed each time I attended the Liturgy. Quite a number of the congregants arrive late for the Liturgy. Sometimes shortly before the distribution of the Eucharistic elements.
Anyone know why this is the case? It made it seem that quite a majority of parishioners are rather....nominal (it just is to me but I can't say for sure).
Not ideal but hardly out of the ordinary historically. Traditionally, Orthodox and Western Catholics rarely receive Communion even though Mass is every week. (In the modern Catholic Church, lots of people receive whenever they come, whether they're prepared or not; not our teaching and a problem.) It's not unusual for old-country Orthodox (or Roman Catholics) to pop into church for just part of the service to light candles, say a few prayers, and maybe socialize/network a bit.
Folk church (not to be confused with church teaching): men are often not expected to participate. Maybe stand on the porch and smoke or pass around a flask of vodka while the ladies do their devotions and the priest does the service, which simply goes on, in Orthodoxy for hours, regardless of the size or attentiveness of the congregation.