I'm a web developer, but in no way affiliated with sams. In the past I have created, grown and managed several forums MUCH larger than sams, and several the same size as sams.
Not trying to be too harsh with the OP but using a forum as your image hosting location is akin to using your hatteras as a ski boat. It's like using a wrench to loosen a phillips head. Will it work, yeah, maybe, kinda, but it's not the correct tool for the job.
Cmon man, it's 2019, get you an image hosting service and while you're at it figure out what video hosting service you want to use as well. Sign up for said service and pay their annual/monthly fee.
To answer you question 'is it complicated', hell yes it's complicated. The wide array of image formats, sizes, orientations coupled with all the different devices that are used to take said pics, not to mention making the upload and organization process easy enough so non-tech saavy people such as yourself can actually use it. Then on top of that, server space and bandwidth become HUGE expenses. And for a free forum to just absorb those costs is not fair. So yes, just b/c it's 2019 doesn't mean that creating a service such as that has magically become 'easy' or 'cheap', it's harder and more expensive than ever.
And to the people asking sams to charge a fee.... do you really want this forum to die overnight???? I want it to be easy and free for people to come here and answer questions and share experiences.
BoatDiesel is a completely different animal. But think of what the membership on boatdiesel would be like if it were free....? I'd guesstimate it would be 10x the size it is today. Sometimes I post a question there and it is weeks before it's answered. Here on sams we get responses within a few minutes usually.
As a second note, why would you EVER want a free forum to be the central hosting location of your image hosting? What if sams shuts down tomorrow? Your images go bye bye. It's like saying you are not going to use your bank to hold your money anymore, you just gonna let the owner of the jiffy store around the corner hold all your cash for you.