I know that the radiant quests Preston Garvey, Radio Freedom and settlers give you are a main cause of frustration in the game and may seem rushed, however I feel that its possible to look at them from a different viewpoint.
One main issue about Minutemen radiant quests, specifically the ones that take place at an owned settlement, is that the odds of triggering one are the same regardless of how well your settlement(s) are defended, fed and watered. This may hint to the fact that the Minutemen radiants were first implemented early in development as part of a more in-depth workshop mode conceptualized by Bethesda. Presumably, a part of this more ambitious incarnation of a key feature of Fallout 4 was that the chance that you were to get a radiant quest associated with an owned settlement depended on the settlement in question's stats. For example, it would more likely for one of your settlers to get kidnapped if your defense stat is less than twice the current population of the settlement.
Due to time, and likely, space constraints, the developers had to water down the workshop system to make it work like it does in the finished product. As a result, the mechanic that allows the chance of getting owned settlement radiant quests to be governed by settlement food, water and defense stats, was cut from the game. The only quest in the category that is influenced by settlement stats are the "help defend" misc objectives in the Pip-boy. The reason is that they are configured differently than the start marked radiant quests; you can get them as long as you have one or more owned workshops with a population of at least one, and regardless if you're a member of the Minutemen or not.
Hope that sheds some light on the nature of the Minutemen radiant quests. Anyone think the same?