Except that hitters can hit 100 MPH FBs these days if they don't have movement.
What made Alvarado was developing the cutter. Hitters could no longer sit on his FB.
What makes Brogdon when he's on is his changeup, otherwise his 95-97 is very hittable.
What makes SD is his slider.
Movement and release point also matter, Wheeler has a long release which makes his FB effectively faster, and when he's on, movement on his 4 seamer. When Nola is dealing, it's about command, not velocity, when he can locate that 2 seamer where it starts off the plate and hits the edge. Same with Suarez, who when he's on, locates a 93-94 2 seamer with a slider and changeup.
What has changed is a 95 MPH FB with little movement is almost like a batting practice pitch these days.
Our former pitching coach(s) didn't understand this, they wanted 4 seamers high in the zone, but for most pitchers, that pitch should be above the zone as a "show me" pitch to move the batters eyes while throwing 2 seamers low in the zone and breaking stuff away.
You can still be effective throwing 91-92 (probably not slower than that anymore) but you need movement, command and two plus solid secondary pitches. Heck, Colon built a long career out of mostly FBs, but he knew how to vary speeds from 85-95. Problem is most pitchers lack the command and secondary pitches to keep hitters off balance.