This is a very strange post that seems to confuse resource cost & action cost but dtill talks about both as distinct things, the two are extremely different things. You may as well be citing the cost of gasoline in reference to the time a particular race car gets on the quarter mile at the track.You keep asserting this in spite of the fact that many people have pointed out that in our opinion, it does include a significant action cost. I think a spell slot is a significant action cost, especially at low levels, and a reaction is a hugely important action cost, especially at high levels. I find it odd that you seem to see reactions as worthless. Has no one in your campaign ever taken counterspell?
Casters rarely have reaction options & even noncasters don't tend to have many absent things like the sentinel feat or niche archetype things like the cavalier. Burning a reaction that was going to burn itself by virtue of going unused is a technicality not a cost. Burning a first level spell slot in s a resource cost, but at higher levels it deflates to a one of no meaningful consequence.