I’d be careful describing a belief to “most” Protestants. Many, many Protestants don’t believe any soul will enter Heaven until the last judgement.
Many more believe that only God (and Jesus if they don’t believe they are the same) can exist in heaven and the promise of Christianity is to make Earth like Heaven. Some of those groups believe that prayers to the dead, including to Mary or the saints, is therefore forbidden or an overt act of devil worship or paganism.
Even more controversial is the idea that the dead can intercede on your earthly behalf. That would be seen as pretty outside the view of many very mainline Protestant denominations.
Many more believe that only God (and Jesus if they don’t believe they are the same) can exist in heaven and the promise of Christianity is to make Earth like Heaven. Some of those groups believe that prayers to the dead, including to Mary or the saints, is therefore forbidden or an overt act of devil worship or paganism.
Even more controversial is the idea that the dead can intercede on your earthly behalf. That would be seen as pretty outside the view of many very mainline Protestant denominations.