Well, @Falco has raised this issue several times in recent memory. There aren’t really that many options, and I think that there are still plenty of folks who are doing just fine with SparkPost. Every test has false positives and false negatives, and you just got unlucky with SparkPost’s test flagging you erroneously.
All mail delivery services have their problems. They are targets for spammers and if spammers use their servers their IPs get blacklisted. I use Mailgun for people when I set up Discourse for them. I frequently get my accounts disabled, presumably because I’m creating lots of accounts from the same IP address. I’ve established a relationship with one of the guys there and have a system worked out, but it’s just a difficult business.
Spammers just ruin it for everyone.