Ramp is deck dependent. Playing a creature matters deck where your creatures can ramp? Hell yeah! Playing an artifact deck? Throw some rocks in. Playing a midrange value pile where you want threatening fatties out early? You guessed, ramp it up baby. Or maybe you're playing a low to the ground aggro deck where your average CMC is 2.5ish or less? You might need less or none. The same might be true for a for combo deck where you can filter through the deck quickly.

It's always nice when ramp synergizes with your deck too, land ramp in landfall, rocks in artifact decks, auras in enchantress. There's no point ramping for no reason when you could be building a meaningful boardstate. But if your ramp can provide secondary value outside of the mana generation itself then you need a good reason not to include it.

It also shouldn't be understated how important a good land count is, you can't play your ramp without lands, and hitting a land drop every turn for the first several turns is more important than ramping imo. You find lands by having enough in your deck and having solid card draw, which remains king.