No, and yes. Alternating the plucking fingers, like most of the tried and tested techniques for playing musical instruments, is about efficiency and maximising musical expression. While M is making the return trip, I is plucking, so this doubles the plucking speed over one finger plucking and makes string crossing more efficient. The result is greater musical fluency. Yes, it is hard, but it is well worth the effort. It will be easier to learn two fingers now, in the early days of your guitar experience, than trying to swap later. It's important to practise it MI and also IM because some passages, especially those requiring string crossing, will require it. I also get my students to practise plucking like a drum paradiddle: IIMI MMIM to open up more possibilities.
As for the Yes, plenty of wonderful music has been made by one fingered pluckers. Many have no choice: they may only have one finger. The bass lines for a significant number of the big Motown pop hits were played by James Jameson plucking with one finger. But why make it hard on yourself?
Finally there is the one finger tremolo involving both downstrokes and upstrokes. This is certainly worth practising, but I'd master the two finger method first.