If you knows little about programming, I suggests that you use WordPress.
First thing, because you outsource things, you will not know how well your custom CMS is coded. Yes, you can see that they are working, but the web that is working is different with the web that is working well. Some coders may have efficient programming, some coders have less efficient programming. If you are thinking big, inefficient coding will drain your IT resources faster, requiring you to purchase bigger server or bigger capacity.
Second, with WP you too can customize things. While coders and designers could do it, in times there are things that we like to do by ourselves. For example, a change in the logo. While you can phone your designers to change it and takes you 15-30 minutes, a change by yourself will only take around 1-2 minutes. It goes without mention too that NOT be dependent on some programmers/designers could be a great idea.
Third, E-Commerce could be easily done by WP plugin WooCommerce. Building your own E-Commerce is fairly difficult, and takes much time. WooCommerce is quite complete, and don't cost a dime. Building a custom E-Commerce CMS is quite difficult, not to mention that most of the coders are not security-oriented. Again, you know nothing about coding, so that some sites could work, but you couldn't discern it whether it's a great code, or just so-so code.
In siloing, yes, WP is difficult to handle.
In authority, there are no differences between a WP site and a non-WP site.
It all goes with what is your main preference.