Welcome to the community @mbdaylight
Yes, that will be your deliverability issue.
I also think you’ll see a poor response when sending from a generic domain, particularly if you’re an ecomm business, even if you get past spam filters. Recipients view these types of emails suspiciously.
The only real solution is to have a branded sending domain and configured correctly for SPF, DKIM, and DMARC. More info on that here: https://help.klaviyo.com/hc/en-us/articles/115000357752
Basically, that set-up lets receiving email systems know that your emails are genuinely from you and have not been tampered with in transit.
The next step is to build your sender reputation - which can only be done with a branded sending domain and over time - by ensuring you focus on your content and list management to maximise engagement with your emails. More info here: https://help.klaviyo.com/hc/en-us/articles/15332906406171
Hope that helps
Andy