The content is the value you want to create. If you content has no value to the user, or if it is duplicate content, your content will not be brought forward. Check content quality, good usage of semantics, still using the most important keywords and variations in the right places, while keeping focus on relevancy for the user and not focus on SEO only.
Content is King, but far away are the times when Google got tricked with keyword stuffing. As Google bots constantly improve to assess your website's content, your site will be penalised in rankings if your content doesn't make much sense linguistically or for the user.
Since mobile first indexation, the content on your mobile version is the master one for both mobile and desktop indexation. This means the content on the mobile version is the one which counts. Space on mobile is more limited than on desktop so choose your content carefully: engage your users, don't bore them with too much content, but enough to guide google bots.
Search Engines do not like duplicate content indexed. If you have many similar pages and you are not flagging them, these pages will not rank well and make your indexation of key pages tricky. Duplicate content can either be confusing for users (and indeed search engine algorithms); it can also be used to try to manipulate search rankings or win more traffic. As a result, search engines aren’t keen on it, and Google and Bing advise webmasters to fix any duplicate content issues they find.
A crawl of your site will help Identify duplicate. It is important then to decide on the master page, the page with most internal links or/and with the best UX.
You can fix duplicate content issues by: Preventing your CMS publishing multiple versions of a page or post. Using the canonical link element to let search engines know where the ‘main’ version of your content resides. Canonicals are best used when you have very similar pages for instance same t-shirt in different colours. You don't want to index the same t-shirt for each colour, although you want to keep the urls for the user to browse through the options. Beware though that sometimes canonicals are ignored by Google so it is important to monitor the results of canonicals implementation and follow up with a new strategy if necessary.
A possible cause for duplicate content is when targeting different territories (UK and US for instance) with different domains or urls but with a very similar content. Make sure then that you have well implemented hreflang!
Often, companies create Landing pages and then expect it to perform as it is. There are actually many factors that will make a landing page work, from design & UX to SEO.
Users need to easily understand your website. They should be able to find what they want in a heartbeat. They should know where to click and how to navigate through your site. Check how the page fits within the website, does it make sense in the customer journey? A beautifully designed website is nice, but you should definitely make it your top priority to create a user-friendly website first.
The importance of the page should be measured by two main parameters: how deep in the website it is (the more important the keyword the page is targeting, the fewer clicks it should be from your homepage), Secondly, the more important it is, the more internal and external links should be pointing to it compared to your less important pages.
The keywords you have selected for the page as the most important should be used for content and general onpage optimization. Make sure another page is not cannibalizing the traffic for the selected keywords(s) and organic traffic is not going to another page instead of the one you chose.
Generic technical issues also apply such as page speed. It needs to load fast and of course be mobile friendly. Finally, the page should be available for indexation and crawlable.