Your question is very general.
I'd suggest you locate people in Clarify which seem to provide useful advice + book calls with several of them.
How you approach Marketing depends on many factors.
Whether you're an introvert or extrovert, to me, is the most important starting point, because if you're an introvert + try to do extrovert-esque marketing, you'll fail.
Extroverts trying to do introvert-esque marketing will also fail.
Also targeting results, to me, is next on the list.
For example, I'm an introvert, able to masquerade as an extrovert for short periods.
So I bootstrap all my new projects using platform speaking at Meetup groups + conferences.
I target acquiring my first 100+ clients for a project via nose-to-nose selling... well... very soft selling...
Having these core users, I then train them... again, so softly, they never notice... to send me referrals.
100 clients will to pay anything, to me, is worth far more than 1,000,000 of random people on email lists.
I'll take profit over numbers of people, any day.
Your question is confusing...what I'm getting from it is you're looking for daily operations pain points in the marketing field to help you focus on what to build as an app?
If that's correct, pick a specific niche (an industry, a business size, etc.) and ask them.
What matters to a medium-sized organization can be gibberish to a solopreneur. Smaller organizations just don't have the problems larger ones do. That's why it's critical to pick your niche. If you build something that improves the way accounting, inventory, and CRM systems talk to each other, minimizing the number of instances what was billed isn't what was shipped, for example, that will be good for larger companies. But solopreneurs won't want it.
The way smaller companies market is different from the way bigger ones do. So focus on the kind of customer you want and the kind of problems you want to solve. My gut reaction is for you to focus on larger organizations, because they are more likely to have the kind of problems at scale that mean they can afford to invest in your solutions. Having a target market that can pay for your help is critical...and a simple point often missed by saas creators.
Every day is different and you'll have evolving challenges during the lifecycle of your products or services. An important first step is taking the time to understand your audience and what value you are providing them or what problems you help them solve. For example, ask yourself how your apps save them time, make them money, or entertain them. Knowing who you are speaking to reduces many of these marketing hurdles. Be genuine, be honest, be consistent, and publish content that has value for your audience. Finally, research apps and services that can automate some of your outreach tasks and provide you valuable analytics on your efforts. And keep learning - read an article each day.