TL;DR It's not personal, it's just business.
One thing you need to keep in mind is that Tapas is a stand alone company whereas Webtoons is/was a subsidiary of Naver (announced last year it would be spun off into its own corporation). Tapas has something like $10M+ of financing extended, some paying as much as 8% yield. Tapas has to turn a profit in order to keep the lights on. Webtoons doesn't because Naver is paying all the bills.
The bias/favoritism is actually capitalism. Tapas is going to promote whatever is bringing in the most income. Wouldn't you? This is why the homepage and the Daily Snack are largely premium series. Premium sales are what keeps Tapas going because ad revenue is largely evaporating.
Webtoons behaves completely different because it doesn't have any financial constraints. It can spend $100,000s monthly on its exclusive series and $100,000 on Patreon pledges because it has a money stream coming from Naver (with a tiny fraction from ads). The big question though is how long will this money stream continue to flow? Also as some have pointed out, just because Webtoons does not appear to have any significant visible income doesn't mean it's not making money. They could be data mining the heck out of its readers and reselling the data to third parties. No one really knows. But taken at face value, how long can Webtoons be a going concern when it's a money pit? Yes it's great for creators, but is it sustainable?
Another consideration you need to remember is that Webtoons has way more readers than Tapas does. Webtoons.com receives 4.5x-6.0x more traffic than Tapas.io, according to SimliarWeb. But that's nothing in comparison to the app. Line Webtoons app is currently ranked #133 in the world. Pokemon Go is #142. There's no hard data but this ranking translates into approximately 15M to 20M daily active users of the Webtoons app. Meanwhile the Tapas app ranks at #2002.
We agree with this statement because Tapas may be missing out on a lot of growth. Right now if a new reader arrives, because there is so much pay-to-read content, unless informed otherwise, a new reader may assume that Tapas is a paid site and leave. Look at the homepage bounce rate between Webtoons (27%) and Tapas (40%). 40% of all Tapas traffic is immediately pulling a U-turn and going elsewhere. Not to say that this is abnormal.
But when taken in in comparison to some of its peers, MangaGo.me (20%), Webtoons (27%), and TopWebComics (34%), the Tapas homepage appears to be lacking a certain "stickiness" that keeps readers on the site. This in turn translates to less readers for everyone, whether premium or free. Unfortunately the homepage is a difficult balancing act between selling product and giving readers what they want. If readers can't find what they want then they go elsewhere.
And that's the crux of the problem. Finding relevant content. Tapas needs to reconsider the reader experience and invest in improving it. At Webtoons the "spotlight" is in rotation, offering 7 titles to Tapas' 1. The homepage also offers genres right away. At Tapas you have to decide between "comics" or "novels" and then find the drop down menu. How many readers are going to figure that out on their first pass? We realize that staff wants to make the homepage and the app match each other exactly, but the website is challenging for first time readers. The harder it is for a customer to find what they want, the more likely they will give up. More genres, an improved search function, and ability to set content preferences for return visits would definitely improve traffic retention rates.