The difference you're feeling is probably real, but not exactly because online tarot is less accurate than in-person. It has more to do with the dynamics of it all. An app generates the cards and that's it - you read them yourself or the app gives you a generic interpretation. With an actual person, they're right there talking to you, listening to the tone of your voice, picking up on energy, asking questions that help put the cards in better context. That makes the reading much more personalized, even though the tarot itself is the same.
Apps also tend to give pretty automatic and broad interpretations because they need to work for anyone. A tarot reader can adapt the message to your specific situation, connect the dots between what you're going through and what the cards are showing. So yeah, it's worth keeping the app for practicing or getting quick guidance, but if you want a deeper reading, going in person does make a difference because of the human interaction - not because online tarot is "less spiritual" or anything like that.