We don't need to be too strict when we say that only people who own bitcoin and have full control over it by storing it in a non-custodial wallet are bitcoin investors, and people who invest in bitcoin through ETFs or store bitcoin using third-party services are not investors. They are all bitcoin investors and all own bitcoins, but the difference is whether they have full control/not full control over their bitcoins.
I'm not comfortable saying that since it can mislead people to believe they own Bitcoin somehow. I think this is similar to how people invest in gold ETF, nearly all of them don't assume that they can cash that out and bring their gold back home because they don't really buy one. At the very least that's my experience with traditional finance in my area. Not to mention buying Bitcoin is way easier compared to buying stock or gold, etc. I don't know, if somebody likes Bitcoin and understands the principle behind it I don't think not fully owning them is a good idea. Just 2 my cents.
I get what you mean but if we take that harsh stance and discourage loved ones from investing in bitcoin or advise people not to invest in bitcoin if they don't store bitcoin themselves. Do you think more people will invest in bitcoin and will bitcoin become as popular as it is today? I bet if there were no bitcoin ETFs, we wouldn't have as many people interested and invested in bitcoin as we do today.
As you can see, the amount of money flowing into the market through ETFs is huge, and even the amount of bitcoins bought by ETFs exceeds the amount of BTC mined every day. That shows that the demand for bitcoin is huge but most people do not want to invest in it directly but want to invest through ETFs because it makes them feel safer in their mind.
We can't expect everyone to be like us and confident enough to store their own bitcoins. By the way, I don't think buying bitcoin and storing bitcoin will be easier than gold or stocks, this is the bias of bitcoin investors.
Put yourself in the shoes of people who have never invested in bitcoin and don't even have basic knowledge of technology, they even have difficulty using the internet, you will see their answer is completely opposite to yours. And unfortunately, such people still make up the majority of the world's population.