FWIW, it’s not just Catholics who have a problem with ecumenical services. The Lutheran Church Missouri Synod, in particular, has a somewhat tortured relationship with other Christian denominations (although other branches like the ELCA are more laid back.)
This is not common, though, at least in the United States. Not that it’s demonstrative of truth, but googling for information on, say, Saint David, turns up a lot more about a Welsh guy than a Hebrew one.
The only “weird” saints that I’m aware of are saints like Michael, the archangel. That is, the guy isn’t even human.
“Protestant” is a very broad brush. Many, probably most, Protestant denominations believe that communion, in their church, is a commemorative act, and that no miraculous transformation of bread and wine takes place. Catholics (and Orthodox, and most Anglicans) would agree with them. Without apostolic succession, the proper form of consecration, and intent, there can be no Eucharist as Catholics understand the Eucharist.
Then there are the Lutherans. From “FROM CONFLICT TO COMMUNION: Lutheran-Catholic Common Commemoration of the Reformation in 2017,” a document published by the Lutheran-Roman Catholic Commission on Unity, a sort of joint commission with the approval and participation of both denominations:
and:
Of course there are still disagreements about form, and about ordination and apostolic succession, but in essence Lutherans and Catholics agree about the Real Presence of God in the Eucharist.
It’s hard to say anything definitive about what Anglicans/Episcopalians believe. As Hector St Clare said, they have a relatively low view of church authority and do not require much in terms of doctrine beyond the historic creeds of the church. I have known Anglo-Catholics who venerate Mary and other patron saints, and on the other hand, very charismatic Anglicans who speak in tongues and hold faith healing services. Not that those two practices are mutually exclusive.
I’m more of a Real Presence guy than an Transubstantiationalist, but Anglicanism (by design) is a big tent.