One of the main issues is the lack of competition. There are now only 3 main browser engines, Blink, Gecko and WebKit. Blink (which poses Chrome and Edge) is by far the largest, and has a the enormous marketing might of Google (and Microsoft to a lesser extent) behind it. WebKit runs Safari, which only runs on Apple platforms and arguably only has the market share it does is because Apple doesn’t allow other browser engines to run on iPhones and iPads. Gecko, the engine of Firefox, continues to slide into irrelevance (which pains me to say as a long time Firefox user).

We are in real danger of the web being trapped in a browser monoculture again, like the dark dark times of Internet Explorer’s dominance. This led to a period of stagnation in web technology Microsoft at the time put little effort into developing IE. Allowing Blink/Chrome to do the same will likely be just as damaging, albeit in different ways - particularly for privacy on the web.

For the good of the web no one company should ever be in the position to dictate web standards, which is why we need a healthy and competitive marketplace of web browsers and browser engines. The problem is that web standards have now become so complex developing an indecent browser engine is now a monumental task. Opera gave up on Presto, once the poster child for browser innovation. Microsoft, a company with far more resources, gave up on Trident. Mozilla was developing a new generation browser engine called Servo, but gave up on the project also.

Constantly moving targets don’t help. CSS, HTML, and JavaScript add new features way too quickly. Between supporting new shiny stuff and crusty old stuff there’s so much bloat to keep up with. It’s taking huge efforts to design and tune these rendering engines, so there are only a handful of efforts now backed by major players (Google, Apple, Microsoft, and Mozilla). Even Microsoft threw in the towel on their own engine and started using Google’s Chrome because it was cheaper and easier.

No one seems to answer the question « why do we need a new one? ». Can someone give his/her thoughts on this ? I’m curious. Are the current engine not good enough?

Theres nothing stopping a new engine from being made. People wanna say its too hard or whatever but there are budding projects people are working on from the ground up. See Servo, Ladybird and Flow for non-Chrome/Firefox browsers. It's absolutely possible no matter what these naysayers say.