Marketing site for a business is simple, use Wordpress until there is a reason not to. Oh I know I said the W word, but it works, it keeps you focused on building your product instead of worrying about building a marketing website.
Now if the product IS the website, then Wordpress wouldn't be the starting point, likely. But even then choosing a stack depends on the problem you are trying to solve. The common SPA frameworks are nice but are not right for all problems, so the problem you are trying to solve matters. No different then what database to use, depends on the data needs.
If its just a business/brochure site or even a "marketing" site for a startup/product with a login button that goes to the app. Then I would recommend trying out a static site generator like Hugo.
You can achieve really great designs, free of the constraints of LAMP CMS templating systems.
While you probably need to know git, if you do, I would say it's much easier to deploy and maintain the hosting than a wordpress site.
If you have no dev skills, not even a bit of HTML/CSS then yeah you should probably go with Squarespace.
I'm a LAMP developer. Marketing sites are WordPress and Beaver Builder. App functionality is the Slim framework with the RedBean ORM or a WordPress back-end.
Now if the product IS the website, then Wordpress wouldn't be the starting point, likely. But even then choosing a stack depends on the problem you are trying to solve. The common SPA frameworks are nice but are not right for all problems, so the problem you are trying to solve matters. No different then what database to use, depends on the data needs.
You can achieve really great designs, free of the constraints of LAMP CMS templating systems.
While you probably need to know git, if you do, I would say it's much easier to deploy and maintain the hosting than a wordpress site.
If you have no dev skills, not even a bit of HTML/CSS then yeah you should probably go with Squarespace.
Go for a bootstrap+ angular/ react template and modify it to taste.
If you need to connect to backend create a service and make rest calls
But if you need more features, my speed stack is jQuery + Bootstrap for front end and Parse Server + MongoDB for back end.
Application - rails