Ask HN: Anyone replaced enterprise email marketing with something self-built?

We're a smallish startup currently paying $150k+ a year for Salesforce Marketing Cloud (SFMC) to send email marketing and trigger email.

The cost of this pains me, and it doesn't help that our campaign manager hates using SFMC's slow / glitchy web app. We have a solid internal data infra and self-built platform, and a highly effective dev team.

I long to just replace the whole thing with SendGrid + React Email/MJML + some cron jobs + a job queue for sequences. And spend that money on a developer's salary.

Has it been done / can it be done / have you done it? Give me some hope (or scare me off!)

Note: I don't intend to actually send the email myself, I'm aware deliverability would suck. For our volume, Amazon SES or SendGrid can do that for ~$10k a year.