This may sound obvious, but forms were created by people who knew what they are doing. What I mean is, a Xing-Yi spear form was created by someone that had 1) used a spear before, 2) understood how to use it best, and 3) knew the common errors/problems associated with using it wrong - lack of power, lack of balance, inability to transition through moves or move with the weapon smoothly, getting stuck, inaccuracy of targeting etc etc
Forms were invented as ways to solo practice and refine skills, and improve on and remove errors.
Great if you know what you are doing and have some 'raw material' to refine ... but what if you have no idea what spear fighting feels like? Have no idea how to visualize an opponent? Do forms help then?
It's really fairly easy to tell if someone doing a form has an idea of what they are doing and what it's for. A personal cringe for me is seeing sword work done by folks that have never used one or have confused how a stick moves with edged steel. Even then there are levels, there are those that have maybe practiced target cutting with live blades but have no context, or those that understand fight tactics but without bladed weapons. I am limited by never having had a sword fight where someone was actually wanting to kill me with a real weapon, or even a challenge match for first blood - and before you ask or volunteer, I'm absolutely OK with that :-) - so my movement will probably look different from someone that has had that experience.
Sonny believed that all preset patterns and forms have a soporific (hypnotic/feel good) effect on the body/mind, and because they begin and end, are inherently glitchy. He believed that patterns can override reactions, and like a song that gets stuck in your head, are hard to undo once ingrained. Which is why he stopped teaching them. On the other hand, he did practice alignment and accuracy a great deal, and used certain movement combinations to refine these, but never in a repetitive way, always using a basic idea and riffing off it.
Personally I love form work and get a great deal out of the practice (perhaps it's the soporific effect?), and think they are great for training full body integration and understanding wave and rhythm, but really they only start to make sense once you have felt the problem they were created to solve or the skill they were meant to refine. Practicing them without knowing the context, and I mean 'knowing' in an experiential sense, might be a head start for when you do .. but perhaps it's not ...?