Have been involved with 2 companies migrations from Heroku to AWS. It all depends on your company resources. In my cases the companies were no longer startups

Have been involved with 2 companies migrations from Heroku to AWS. It all depends on your company resources. In my cases the companies were no longer startups and could afford to staff Platform/Infra teams and build out a bespoke solution on AWS. This was an area the company wanted to invest in. If you're still a legit startup where money/dev resources is tight, I would recommend first looking into one of the Heroku clones/competitors.