JF- “(Too many commenters here have been saying things like “well, we can’t judge them, and they may be tinok shenishba, but nevertheless, they’re apikorsim!” which seems very backwards to me– I don’t see how a person could be both)”
Rav Moshe Feinstein in Igros Moshe says that you can be both. I don’t have a sefer on me now, but you can look it up. I think it’s in a Tshuva about saying Amen to the bracha of someone conservative or reform.
The reason why you have trouble seeing how someone can be an apikorus and a tinok shenishba is the same reason that you think it is better to be reform or conservative than unaffiliated.
The reason for both of these things is that you don’t realize that having Emuna is a Mitzva, and lack of Emuna is an Aveira. So while it’s true that it’s better to keep some Mitzvos than not to keep any, it is better to keep the Mitzvos of having the right Emuna than to disregard that Mitzva and keep others.
Also, you can keep the Mitzvos that C and R people keep without being c or r. That is what people in Israel do.
This also explains how it’s possible to be a tinok shenishba and an apikorus at the same time. This is because an apikorus is someone who is “oveir” on a particular Mitzvah (the Mitzvos of having Emuna). Just like someone can be a Tinok Shenishba and a Mechalel Shabbos at the same time, he can be a Tinok Shenishba and an apikorus at the same time.