Cinque Terre in late October

Im afraid "worthwhile" is in the eyes of the beholder. There are pros and cons. The biggest pros will be the drop in crowds as the month progresses. And temperatures should fall into more comfortable levels compared to summer. The cons might include shorter daytime hours, especially with daylight saving time ending towards the end of the month. And October is one of the rainiest months of the year, so hiking and trail walking may be affected. But with the crazy weather lately, predicting what October will be like falls squarely in magic 8 ball territory.

We were in the Cinque Terre in mid October a few years ago with RS Village tour, the weather was good although it had rained the day before we got there, the villages were extremely crowded.

Yes! When I visited Cinque Terre it was the very end of October/start of November. It really was the very end of the season- in fact the place we were staying was shutting for the season the day after we left. It was absolutely not crowded at all- we were some of the only people there. This was in 2016, however, so it's possible this time of year is more crowded now. We had been planning to walk the coastal path but at that time most of it was closed due to rockfall so we walked a bit but wound up taking the train between the towns. The cons were it did rain a bit, but on the plus side we really did have the place to ourselves. So, for me personally, I would say it was definitely worthwhile.

If you've never been it will be worthwhile.

Just be aware that the end of October may be rainy in Italy, even torrentially rainy (especially Liguria, for geographic reasons), and in case of rain, the hiking trails will not be accessible because the National Park closes them for safety reasons.

Whether the place will be very crowded or not will depend on the weather, and also whether there are cruise ships docked at La Spezia on those days you go. On weekends there are also many Italian day trippers who go there, weather permitting.