Yes, mostly personal but I think I agree with your opinion across the board. Others can and do certainly work but the best flag can only show you what has already happened. The closer to real time, the better, basically.
You have to watch all the flags on the field as much as you can, too. A point of reference in that regard is that a 10mph wind is moving across the range at 14.6 feet per second. So, if you and your neighbor's flags are 15ft apart, you have 1 second to respond to what they just did, MINUS their reaction time, which can be that much or more poorly designed flags...no other influences! Done right, reading flags has us all fighting over some fraction of 1 mph without getting caught in anything, so every little bit matters. Adding things to the flag adds weight, of course, and that slows their response time and ho well they stop or start with the wind. Lots more to them than that but that alone gets your head on straight and the rest is THE fight that we are all trying to do better than the others on that day. The old saying "the wind is my friend" is very true! But you don't have to like the wind much...just more than anyone else you're shooting against on that day is all. Lol! Flags are way under rated in terms of priorities on our equipment, IMO. Most anyone that shoots seriously will tell you that the wind determines who wins or loses on most days but you still see some pretty much terrible homemade or otherwise just poor quality flags very often. They might be the single most important piece of equipment and I don't think of that as a smart place to skimp in this game. Like many items in this game, if you cry once, you're probably on the right path as opposed to buying and selling only to wind up in at the same place except you spent too much time and money on crappy flags, stepping over a dollar to pick up a dime kinda thing.
We don't mind spending big bucks on a rifle, rest, bbl, trigger or whatever but when the rubber meets the road, wind reading is at the top in regard to who wins, more often than not.