I think it is an issue because, people browsing your site in other languages will have the wrong language title displayed in their browser tabs if they are multi-tab browsing! The title tag is still one of the important ones for SEO, nothing has really come along to replace it
A businesses' ambitions in terms of an international roll-out, are to break into new (foreign) international query-spaces and get extra traffic (especially from Google, or leading search engines in other nations like Yandex and Baidu). Google's ambitions (when adding your international pages to their index) are that their audience can break onto other areas of the web which (due to the language barrier) were previously closed to them. But they want your content to then be 'tailored' to their international audiences, traffic which Google has no obligation to send your way. Google wants good UX for their searchers, so that Google remains top-dog in the search world
The less tailored your international roll-out is, the more shallow it is (with more pieces missing), the less confident Google will be. They will be less confident that sending their users to you will result in positive search-sentiment
Every piece of the jigsaw which you are missing, counts against you. It makes your international roll-out look more like a quick Google-translate powered land-grab, and less like an authentic international roll-out
My question to you is, when you identify a bad signal - why carry on sending it to Google?
Search is a competitive environment. If there are thing you won't do, others will