Creatures have steadily grown in power while non-creature spells have fallen in power quite a bit. The designers of the game concluded that making the game more creature-centric lead to more interesting gameplay decisions. Power level overall has been trending downwards if anything.
My modern deck plays entirely creatures, and entirely humans. It has duress, thorn of amethyst, nevermore, and into the roil main, with the option of getting disenchant, rule of law, and electroylze out of the side... as humans. It's effectively made spells obsolete, since the spell you want is probably a creature now.
- increased the cost of blue spells that counter creatures, because new players get sad when their monsters get countered
- started giving evasion abilities to many more creatures, since new players get sad when their monsters get blocked
Power creep is real. If you remember the days when Savannah Lions was highly efficient, you're in for quite a shock.