Work problem IT

Hi, I work at a software company and recently I've been in danger of loosing my job. I've been developing (alone) a small shopping website in Vue.js (fullstack) which took about 3-4 months. My team work in scrum and everything I have done have been approved along the way daily. In hindsight my boss's boss think I have wasted too many hours on this , and hes critiqued me for not using best practice, I think he wanted me to use a CMS instead.

Are really CMS's best practice? I find this hard to belive. I have a Msc. in Computer Science. sincerely,

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