D&D is the gateway game that brings in new players, and sometimes these players try other games, or discover games they like better. Many companies claim that their success can often be attributed to the popularity of D&D. It's delicate balance, however, because if D&D swamps the industry too much, smaller games can struggle to stay afloat. Kickstarter has been a boon, but there are worrying signs that 5e may be swinging into a phase of hurting more than helping other companies. The hobby needs variety.
The frustration that some of us feel, is that D&D has never objectively been a particularly well designed game in any edition. It's fun, serviceable, and easy to find, but it's not groundbreaking, except, of course, for launching the idea of role playing. I totally understand Aldarc's frustration with gamers wanting everything to come out as 5e, or refusing to try other systems, or assuming D&D has locked down the best the hobby has to offer. It's frustrating seeing supposedly experienced GMs on You Tube unfairly critisizing a game, simply because they have little experience outside D&D, so aren't really grasping other mechanics. It can be maddening watching someone try and twist 5e rules into a genre it's not suited for, but refusing to use a system that will better serve their needs.
And yes. people are free to play what they want, and if that's 5e exclusively, who are we to argue. Sometimes, however, you just feel like crying about all those missed opportunities.