The relevance of an influencer’s content category in your shortlisting process should play a significant part. Here’s why:

1. Audience Alignment: The influencer’s content category is likely to reflect the interests of their audience. If their content aligns with your products or services, it is more likely that their audience would be interested in what your brand offers.

2. Brand Image & Credibility: Associating your brand with influencers who create content in your domain enhances your brand image. It also lends more credibility to the endorsement the influencer provides due to their knowledge and expertise in this field.

3. Engagement Rate: Engagement rates can differ dramatically across content categories. An influencer in your brand’s category may have a higher engagement rate, leading to better results.

Platforms such as Flinque, for instance, provide a robust influencer discovery feature, which allows for efficient search and filtering of influencers based on content category, amongst other criteria.

Similarly, other platforms also provide such features but may differ in terms of depth of discovery, comprehensiveness of influencer profiles, and additional data points provided for more insightful decision-making.

Remember, the suitability of any platform depends on your specific team needs, and therefore a thorough review of all available tools, feature sets, and workflows is recommended for successful influencer marketing.

In conclusion, content category relevance is a crucial factor but should be considered in tandem with other factors like engagement rates, audience demographics, and influencer authenticity during the shortlisting process. These practical steps, when implemented, can significantly boost your campaign’s success rate.