Well, most people I see did have other plans before they retired, but when finally retired and having no one to force them to do anything, they actually do nothing. The hobbies they complained they had no time for, the charities they wanted to work for, etc all quite rapidly vanish. Smart people with high profile jobs who end up watching tv and doing the odd sudoku puzzle. New generations might be different (although I cannot imagine the much reduced attention span of people helps against this) and ofcourse this is anecdotal but I do see this a lot. I know people who are now retired 10+ years and kind of assumed they would be dead by now while they ofcourse have 20 years more probably. At least 3 I know died over 95 in good health (for 95) while being bored shitless (travelling, which somehow is a retirement obsession, apparently gets boring too) for the past 15-20 years.
Being self-motivated is actually incredibly difficult. Just ask any PhD student who has hands-off supervisors. Learning to chase your own goals independently is a skill you have to cultivate. You need to learn your weaknesses, what tricks you can employ to get working, and what you actually care about enough to achieve.
Hmmm there is a market for self-motivation advice to PhD students but they aren't exactly a wealthy audience, and atleast some of it is purchased by education institutions rather than individuals. Beyond that, there are plenty of motivation oriented smart phone apps and etc. And there is 80,000 hours who sometimes take that as their purview.
I'm a 1000x more productive when I have a support group that I spend time lots of time with. Usually that support group comes from being at the office with co-workers. If I retired and didn't find a support group I'm pretty confident I would not stay motivated.
It's not just having people around either, it's shared goals and shared responsibilities. I'm more productive when I know others need my work. We could be collaborating on a game at a game jam where the game designer needs me to add some new settings they can tweak and the artist needs a way to get some new data in the game and iterate. That pressure is very motivating for me.
But, for me at least, it's both the feeling of wanting to provide solutions for other team members, the feeling of a shared goal, and the feeling of camaraderie I get from actually being with people (vs being remote)
I've been lucky the majority of projects I worked on were things I wanted to work on and see succeed. I can imagine lots of projects where I wouldn't feel that.
What you describe sounds roughly similar to what parent op is warning about. Being reliant on external forces for your own happiness / fulfillment will probably suck in retirement - people generally lose friends, not gain them over the years. Find something that motivates you on its own, regardless of anybody's else involvement.
For me that would be travelling, hiking, and generally being in nature - but this requires at least OKish health for the age, which might or might not be there later. Reality is, we mostly don't know how things (and us) will turn up later in life, and if we end up in good spot it will be mostly by sheer luck.
Besides really bad ailments which restrict you to a bed or location or when your brain gives out (the worst option, but yes, it of course happens; stroke, dementia, etc), I try to build on two things; a) hiking/nature b) brainy hobbies and I try to combine them. I read/write parts while hiking, I program parts while hiking, I interact with my friends while in the middle of rainforests etc. If the a) falls away because of an ailment, I am perfectly happy doing b). I consciously try to prepare for the future as I have seen too many unhappy people and that really is so not needed.
the advice I lean toward is that you need to make an effort to have strong relationships and people in your life rather than find ways to learn to be strong without them.
When you spend years going to work every day in the presence of external sources of motivation (a boss who could fire you, a mortgage to pay, coworkers who depend on you, etc.), it's easy to underestimate just how much of a factor those sources play. It's quite difficult to have to rely entirely on intrinsic motivation to get things done if you don't have a lot of practice doing so.
Yes, that's exactly true. We need education to step up teaching people to enjoy solitude and not get instantly depressed/anxious and 'learn' how to have and enjoy hobbies. for both retirement and universal income.