
Yes — Nikko is worth it for two things Tokyo can't match: the lavishly carved Toshogu shrine and genuine mountain scenery (waterfalls, a highland lake). The honest caveats: it's ~2 hours each way, so it's a committed day, and you'll likely have to choose between the shrines and the mountains rather than savour both. In autumn it's one of the best trips in the whole region.
Shrines first, mountains after — timed to dodge crowds.
Open the itineraryYes — for the ornate Toshogu shrine and the mountain scenery of Kegon Falls and Lake Chuzenji, especially in autumn. Just plan a full day and pick a focus, since it's about 2 hours each way.
Nikko is grander shrines and bigger nature, but farther and a longer day. Kamakura is the easiest, Hakone the best for onsen and Fuji. For autumn colour and mountain scale, Nikko wins.