Just going to make a note on this in case anyone sees/cares. I’ve made a lot of grids recently and I think they’re pretty fun. Not world changing or anything but a bit of fun for people to hopefully enjoy doing a puzzle for 5 minutes in their day.

On all of them, people have given them low scores and not bothered making any comment as to why, let alone leaving any comments about enjoying it or saying thanks or engaging in any way, other than to click presumably one star or two star. I would love to know what it is about my grids people hate so much, but I would more appreciate someone (anyone) taking the time to leave any sort of interaction other than a low rating.

It’s dispiriting enough that after 5 or 6 days of this I’m just going to stop making them. Thanks very much.

Great grid for a film fan like me. Keep up the good work, Eddie.

Hi Eddie. Even if there were no changed letters I would still not have got any of these, because generally I don't know or care much who the director is. I spotted a few titles, and even that letters were changed, but neither knew nor cared who the directors were. So I spent a lot of time looking for letters changed in the same position, or the same letter changed, etc.
If you want to write walls for film anoraks, go ahead, but be prepared for low scores from everybody else.
It is nice that there are no hard and fast rules, and novel grids can be a delight, but a good general rule is that a good grid is one which can be solved by someone with a reasonable general knowledge, intelligence, and the ability to make quirky connections.
When I commit to spend 3 or more minutes of my time to solving a puzzle, I expect to have some chance of doing so. If I fail to connect a group, then when I see what the connection was, my reaction should be "arrgh I should have spotted that!". But if the connection is hopelessly niche, the reaction is simply annoyance.
If you are hopelessly committed to film topics, maybe you could restrict that to one of the groups instead of all of them.
Please consider this to be constructive advice rather than simple whinging. You asked for an explanation, and this is my best attempt to respond.

Agree too specialist for me although I appreciate the effort and the thinking behind them, perhaps should be rated as fiendish