I think you are one of the noob which dont know about PHP.
PHP is an evolving language. That I will come to that
Answer to each of your statement
"Extremely difficult to manage as it not very modular."
A: Well look on Composer, Symfony2 Zend, Yii, Laravel, these are package managers and framework designed to work as a modular architecture for PHP
"PHP is interpreted, hence PHP websites are slow unless proper caching management is implemented."
A: Yes it is. But it is the fastest of most of the interpreted language(PHP7) including python and ruby. It is very much used in Hightraffic web applications. It does has long running servers with ReactPHP, AMPHP etc.
PHP8 is going to be JIT. So it is one of the few language that is evolving.
"PHP is not strongly typed"
A: PHP7 supports is strongly typed. so is future version
"No multi-threading"
See pthreads.org
php.net/manual/en/book.posix.php
"No background threads or asynchronous execution of jobs"
A: Swoole (Faster than NodeJs, sometimes closer or more as GO) the rest ReactPHP, AMPHP (built on top of inbuilt features of PHP)
"Some of the PHP functions are horror like eval"
A: May be thats why PHP still used by top companies
"Confusion between objects and associative arrays"
A: One of the weakest argument I ever hear about a matter. The visible differences are clearly seen.