Of course. Check the cedh decklist database – lots of those decks run an average cmc of below 2. Even if I grab my more casual lists – my Kykar Equipment+Vehicle list, running some bigger equipments and vehicles even, bigger creatures and stuff, is running an average CMC of 1.85 over all 100 cards and an average of still 2.9 if I only look at non-lands. It is a list with several 6+ drops, so that pushes the non-land average up a bit, but 2.9 is very high. My Muldrotha list, running demons and other fun stuff, averages at 1.58 including lands and 2.48 excluding lands. And both are quite casual decks. Yeah, they actually do work and have a punch, but they are far from cedh. But I would count both of them more in the battlecruiser category. Even my Locust God list that runs a bunch of dragons / sphinxes and big wheel and twister spells runs an average 1.89 with lands included and 2.89 without lands.
My worst offender is my Golos Turns deck with 2.3 average cmc including lands and 3.8 excluding lands and that list is decidedly bad and “unfair”, as Golos cheats on mana. The deck is centered around Golos cheating and around extra turns with having all the mana available again and again and multiple “untap all lands” effects to reuse golos ability. But yeah, kill golos and it turns into a durdlefest and doesn’t do anything – and that’s why I keep my lists lean and fast.
My cedh Kenrith list runs an average of 1.34 including lands and 1.93 excluding range. And it doesn’t even run Ad Nauseam. But it easily could. My budget cedh Ukkima list runs an average of 1.26 including lands, 1.22 excluding Ad Nauseam (as you will never see AdNaus when playing AdNaus) but still including lands, and even excluding lands it runs 1.89. So I am guaranteed to gain a ton from an early AdNaus when my life total is still up.
You want your average CMC low and you want a curve that maxes out in the 2s or 3s and not the 4s, because you want to play your spells and you want to play multiple spells. Most stuff you play is cheap stuff, the bombs are just that – bombs you play late. And it is not a question wether you “can do that”. You have to, if you actually want to really play before T4. Sure, if you are in a “lets ramp until T4 and then smash big dumb creatures into each other” meta, that’s totally fine and all power to you, but even then I would probably lean more towards close to CMC 2 including lands and having just a small section of my deck dedicated to those big dumb creatures and most of the deck dedicated to cheap draw, cheap interaction, cheap mana dorks and cheap mana rocks.
Last example: I have a Syr Konrad list. Base don Commander’s Quarters budget Syr Konrad. That list got a bit updated, but mostly replacing similar cmc cards, just for more expensive cards that deliver more oomph. It runs an average CMC of 1.84 including lands and 2.84 excluding lands. So yeah, it is more heavy than most of my lists, but still – average below 2 including lands is a good place to be, or at least around 2. And an average excluding lands below 3 makes sure that you actually can play stuff on curve.