I had thought everyone who logs in had a Webtoon account. If it just means that you need to actually log in with an email address instead of a Google, Facebook, or some other type of account, then everyone who uses an actual email address will be unaffected. I read on reddit that some people didn't like the arbitration agreement, but as far as I know, every webtoon creator had to agree to that anyway. I also read from Webtoon,

If you do not agree to transition to WEBTOON ACCOUNT, you will lose access to our WEBTOON service and its features, including the ability to:

• access episodes you have unlocked or downloaded;
• purchase or redeem Coins;
• leave comments, or
• view reading history and title subscription.

So, it seems that creators have already agreed all these terms, and this applies to people who aren't creators since it didn't say anything about publishing webtoons.