Going into code frameworks discussions is kind of missing the point IMHO since they require development, time, money skills beyond what a typical user can do.
WordPress is popular indeed, and require a bit of a mechanic or at least hobbyist spirit to work with it, and I doubt many dealers are going into it alone/without skilled agencies selling them onto a WP based solution, and then supporting it for them.
At that point, the difference between this setup and packages provided by automotive marketing companies might be the depth of expertise on the platform itself.
Is an agency able to modify WP's core if required? It's unlikely (and not really advisable), some build plugins (We did just that for WP with to market and
search engine optimize sites networks from the cloud. One of these
marketing automation plugin is free by the way), and most just install and configure plugins trying to keep their clients out of trouble.
In that context, an organization that actually control their product core and service directly their client might be the ideal better bet for dealers.
They're
alternatives to WordPress listed on this site, including some open source and free ones that might be a good fit for dealers. And these companies not being the size of WordPress, have also a direct service focus, which means you might be able to get the best of both world, a free/open source system that let you change service provider as needed/not being locked-in along with direct support from the actual product manufacturer (called sponsor in open source product) who has the depth of expertise required to make anything happens, including upgrading system core, and developing innovative solutions driven by the needs of an early adopter client.
