GetResponse - lightweight alternative?

I have been using Getresponse for nearly 10 years. In that time, they increased the subscription fees multiple times, with the service having become worse. In that time, they added a ton of tools to their software, none of which I use. I use basic autoresponders, and a few simple automations, which I could solve differently if I had to.

I just had a bad experience with them where they blocked my account in the middle of the night, cause they couldn't charge me a list extension fee for being 42! contacts above my plan limit for a few days during the last billing period. No warning, nothing. Just immediately blocking the account, despite being on a 24 months plan. Essentially saying, pay us more now, or you cant use the service you already paid for anymore. Most tools these days send you a warning when you get close to the limit, or let you decide if you want to pay extra or have features limited once you reach the limit. Getresponse just rubs their hands and is happy to immediately slap you with a list extension fee that might in some cases cost you more than your normal subscription.

I had been thinking about switching to a newer, lightweight provider for a while. For my transactional emails, I already use AWS. I was considering just coding my own lightweight autoresponder, or if I should pay for a new tool. What tools do you like and recommend? Something that only does simple email marketing and autoresponders, without feature bloat, but does it well