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I understand that Presto it's not Chromium and they should rewrite every feature, what I tried to explain it's, if you have something really good, why did you leave? Even with the "what kind of users they want" they should let Opera for Opera for real, that's why Vivaldi exists, ...
Because the rendering engine (whether Blink or Presto) is what first 'touches' and interprets the website's code to turn it into something that an interface and display layer can make use of, there must be very high compatibility between how the rendering engine operates and what the site code designers have written. However, not all rendering engines will operate the exact same way against the same web code. Website code can be (and is) written and tested by website designers for maximum compatibility with how only the most popular rendering engines are known to operate.
Unfortunately, if the rendering engine (eg: Presto) and its adopting browsers don't command a major market share, website designers won't code for compatibility with it - in fact, they may actively "sniff" for the less-popular rendering engines and intentionally cause their site to refuse to operate with them at all to avoid user mis-functionality complaints... hence the commonplace website listing of "supported" browsers. That means a browser relying on a less-popular rendering engine design must support its own extra overhead costs of constantly attempting to create workarounds and spoofing mechanisms to fool such sites in order to allow maximum user site access. Employing Presto, even with some of its flexibility features, put Opera ASA into that position over and over again. It's also one of the reasons Vivaldi chose to go with chromium/Blink as well, in order to avoid the overhead expense of constantly having to deal with their own custom rendering engine compatibility issues.
