In my experience, you can't change mindsets without proven results from changes made by others.
It's the same as whether or not a business sees "value" in a professional designer.
There are a buh-zillion business out there with someone untrained using Photoshop and creating their marketing materials. That works for them.
They won't change that mindset until it is proven that a trained professional actually does result in better Return on Investment (ROI).
This means testing. Same product/service, same copy, two (or more) entirely different marketing approaches.
Many knowledgable companies will test marketing and then have cold, hard, ROI data and they can see what actually works better. However, for many smaller or budget conscious companies, testing isn't something they are willing to explore.
As a further example, when dealing with sales related design, a company can look into Acxiom Infobase Data. What this does is provide a very detailed demographic breakdown of your consumers. (Yes all that data the internet collects on you is somewhere and being used.) For example, using Infobase a company may find it's consumers are....
- Primarily Males
- Affluent: 48% of your buyers make over $125,000 per year.
- Cash Available: 80% have over $20,000 in savings.
- Age: Primary 55 to 64 / Secondary 35 to 54
- Educated: 56% have completed college
- Home Office: 51% work from home
- Interested in Self Improvement
This data can be invaluable for sales-related design. However, there's a fee to acquire such data. And just like changing mindsets regarding a design, you can't convince a company this data would assist them in getting higher ROIs until they see it.
If you have such demographic data, then it's often feasible to create a compelling argument as to why current design models are failing. i.e. they are too male focused, they "look" too pricey/low budget, etc.
While the example here is based on individual consumers, the same general data can be acquired for businesses.
Ultimately though, it is often a leap of faith on the client's part initially. And really, that's generally the best you can hope for. Without hard data to build a case against current design models business owners tend to be scared to change for fear it will lower ROI. .
You could possibly hope for some personal connection a business owner may have to someone who does understand value in something - who can then sway the owner. As an outside entity, it's nearly impossible to convince a business owner that marketing could be improved by being "different" than the "herd".
One thing about many business owners I've encountered is they are risk adverse when it comes to their bottom line and only when things are going well for them would they ever consider something new to "test". Unfortunately, when things are going well, seeing what may work better is often the last thing on their minds
By all means present something different than their "norm" with your opinions and reasoning, but 99% of the time it'll be shot down. There will be that 1% that is willing to take the leap though.
All this is much easier if you have an established relationship with a business over a period of time or via past successful projects. If they've been happy with your work, and then you present them with something which is outside the customary purview, there's a greater chance they'll listen.
--- I have no affiliation with nor do I endorse Axciom Infobase directly. ---