Digital marketing pain points

Hi all! I'm doing a bit of research, and I'm looking to hear from people that are having issues with scaling their digital marketing efforts. Here's a few questions I'm looking to answer:

• What would you say are your biggest challenges in this area? Would it be dev resources (splitting time between front-end/back end, for example), or high level channel-specific expertise?
• Is there any issue with demonstrating impact, such as channel attribution?
• What is the area you find most challenging, such as content strategy?
• What kind of insight do you think is lacking from your current digital marketing activity?

A few things to keep in mind:

• This is for non-drop shippers. Looking for businesses that source direct, hold stock or manufacture etc.
• Ideally revenue above £300,000/$0.5 million. The challenges here are different to bigger/smaller stores
• Obviously growing revenue is a big challenge, but I'm looking to understand what is stopping marketing campaigns from performing and hitting this goal

Thanks everybody!