The "notoriety" in part comes from issues during development of new xpacs and in part from hyperbole like this. Let's separate the simulation mechanics from the specific profile. The profile that simc uses is
not a BiS recommendation. This particular profile was built early (e.g., before the Relic was nerfed), and was used for dps matching and validation between femaledwarf, Blizzard, and simc. I and others rely on the community to provide good profiles, and we'll happily take improvements.
SimulationCraft is generally quite accurate (and indeed has found bugs and revealed issues to Blizzard); the exceptions are memorable mostly because they are exceptions. Female dwarf and SimulationCraft use different simulation mechanisms. Because femaledwarf estimates the results using formulas, it is generally quicker to update with changes. Because SimulationCraft runs the events of the fight (averaged over thousands of simulated fights), it takes longer to implement and requires more effort to use, but can provide a lot more flexibility and accuracy. For example, it's hard to accurately model haste effects, stacking buffs, RPPM behavior, probably the re-origination trinket in the kind of sim that femaledwarf uses, whereas they can be accurately modeled in simc. Similarly, simc supports multiple fight scenarios, changing priorities in different conditions (e.g., CA or execute range), different amounts or human error, etc.
But the mechanics are entirely separate from the profiles. Your specific objections above are solely gripes about the profile I happen to use (plug it into FD and you will get similar numbers). When I stumbled across this message, I grabbed your profile, removed level upgrades (which we don't use in T14H profiles), reforged, and checked it in instead. I reforged for Crit > Mastery > Haste for BM and Crit > Haste > Mastery for SV and MM (because that was better). The result was BM 126586, SV 120707, MM 118489. So thanks for the profile update!
We now have T15 support in "review" state, which is to say we believe it's correct, but it will lag announced parameter changes (e.g., it doesn't have the chimera reduction from +50% to +25%). I discuss on EJ how you can apply those form the command line. We'd be delighted with reports of specific inaccuracies (e.g., pet Bite is too high) or recommended T15 regular and heroic profiles (as with the T14 profiles, the ones there are adequate placeholders). Also it may be that mmo-champ is a good (or better) place to generally solicit profiles examples. Thanks!