I do not think that PHP7 is poorly designed. Actually I think that PHP7 is the best PHP version so far in many aspects.
PHP had a period of stagnation - after 5.6 was released we waited a long time to get something new. In a meantime, other languages took forward and from that perspective, PHP looked a little bit obsolete. But soon after first stable RC versions came out, the amount of work they put into is just amazing, and results speak for themselfs.
Many new features were introduced in PHP7 (you can see a bit here: blog.feryn.eu/php-7-is-now-available-new-features…). And features are not the only thing - the speed of PHP7 is just amazing. Especially in crowded hosting environments you can see progress.