TLDR: Kill times are long enough in Apex, which is part of what makes it unique in the BR genre, but the Evo at it's highest tier is both too easy to achieve by end game and too strong for the already lengthy kill times.
One of the toughest things about Apex, IMHO, are the kill times. Hitting most of your shots and having to reload your magazine so that you can pump even more rounds into the enemy just to get a knock is a challenge. Rewarding eventually, especially for people that have the skills to stay on a moving target, but it does feel like a lot of work. For some people, even some of the more popular streamers, this is the main reason they don't main Apex or play Apex hardly at all because it has the longest kill times out of the BR genre. They also want those quick kill twitch shooter one shot highlights that Apex isn't really designed to deliver often.
Insert the Evo and now we're looking at even LONGER kill times. Especially with a bunch of red Evos in the final circles. If my opinion isn't shared by most of the player base, and Respawn throws Evos into the default game, I hope they at least consider raising the damage needed to buff the Evo through it's tiers. Especially the Red tier. Hey, if you've done 2000 damage with an Evo and you've made it to top 3 final circles than ya, you earned it. As of now I think it takes 900 damage to go from base to red and I think that's too low for the current kill times.
I thoroughly enjoy Apex in its current state. I have been playing weekly since launch, every season, but wouldn't mind an LTM where we try out maybe an X% decrease in armor/kill times just to see how it feels. As a long time Halo player I've always preferred the longer kill times as opposed to the CoD experience, even though I enjoy twitch shooters as well. That said, I think if the kill times were lower than they are now then the Evo would make more sense if added to the main game mode.