Its impossible to know what people actually meant without an example, but when I read that reply, I think of a "Feature" as an incremental improvement in existing products. That improvement could be unique, it could be pulled from existing other businesses/industry, or whatever. The main reason a feature is "bad" is that its indefensible, and/or minimally differentiated.

To take a detailed example...
Take music services - Apple Music vs Spotify. If you build "Spotify but the pause button works different" then thats a feature. Most likely, the idea is not so special you can pull customers away from their existing solution, so you won't make money (minimally differentiated). If you do have an idea special enough to steal customers... well, any one of the existing competitors (who have more money, talent, resources, business connections than you) can build it before you grow enough to be a threat (indefensible).

A actual business has to do something different on a business level not different on a product level. If you're competing with iTunes and $.99 songs and you offer music streaming (eg you're Spotify)... thats very different (NOT minimally differentiated). People would pay for that, and its not "itunes with X" its a completely different business. Your competition can't dramatically change their entire business overnight because that would scare shareholders and because big businesses don't change that fast meaning no one can copy your idea quickly (NOT indefensible). Of course as we all know, even Spotify still faced competition eventually from Apple Music, but they were able to build a business and acquire MANY customers before apple caught up. Have you heard of Rdio? They were my first used music streaming service and my favorite. They arguably had the best UI and I think they were the first to allow you to use one client to control music playback in another client. They don't exist because their only value was a few features... which wasn't enough to build a business.

Today, music streaming as a whole is a feature that big companies offer as a perk for their other products (see YouTube music, or Amazon Music), so its probably a bad industry to start a company in if you want to "build a better music streaming service", because any change to the service is just a new set of features.

As another example, take personal mobility - in the US cars are dominated by a few big conglomerates that make many shapes/brands. No one can create a car business by making cars that are "basically fords but purple", but (1) Tesla could make make their cars unique enough in features to compete because they had unique electric car technology and the Elon-musk influence that existing car companies couldn't replicate (defensible tech/social moat) and (2) companies invented eBikes and scooters to compete with the mobility problem, but a different product to solve it (differentiated) where they wouldn't experience incumbent competition before they became successful.

> years later I still don't see the type of product I'd put together in the wild.

Someone in another comment said "Perhaps [your idea] replicates 100 things they’ve seen before but adds 1 thing incrementally" - I like this phrasing. You basically need to convince people to pay you for just that 1 thing, since the other 100 they already pay for and are familiar with. If your "1 thing" is 1% of the product value... sorry no one is willing to handle switching efforts. If your "1 thing" provides outsized value... then the existing competition will steal your idea and your only hope is that you grow fast enough to be a real competitor before hand (thats why people take VC money). Thats the problem with being a "+1" - you're either insignificant, or you just performed free market research for a very well funded org that will now compete with you by building that +1 themselves.

IMO if you have a really great 100+1 idea, build it and hope to sell it to the people who built a successful business around the first 100. It may be a good idea that just didn't have any business traction to exist. You could always try your hand at "creating a feature" - people may buy you instead of competing, so thats a nice "exit" for you if you want that. Most people don't want to build a business they need to run for the next 20 years anyways, so no shame in building a vision and selling it off.