Small business with a large email marketing database needs a CRM for email marketing, social media posting, automation

I just picked up a new client who uses Go High Level for their marketing. I hate it. I don't think it is intuitive, I don't know why, but half of their emails have been created using HTML, customers are in Accelo, but Accelo doesn't communicate with Go High Level so I can't easily use anything around "became a customer" as a trigger for automation. It's so frustrating.

I love HubSpot but because they have a database of over 150,000 people, the cost becomes prohibitive for them as a small business. They send approximately 1.5 million emails per month (I haven't yet cleaned up their data base so that number could potentially decrease). Because of the large number of emails, even other CRMs, such as Agile CRM for example, get up into the HubSpot price range.

Does anyone have any CRM Suggestions? I need to make a recommendation this week to them.

TYIA!