"1) does this mean I can’t upgrade my os to Catalina because my Adobe product won’t work with Catalina? "
Your Adobe product will not work with Catalina
"2) Does this mean Adobe 2017 isn’t compatible with Catalina or its replacement?"
(a) no Adobe product is yet certified as compatible with Catalina. WAIT.
(b) Adobe have indicated that both Acrobat DC and Acrobat 2017 will get updates for Catalina if they need them. The key reason to subscribe (I could have explained this better) is that Acrobat DC includes future upgrades, and Acrobat 2017 will at some point be replaced by a new product (who knows, Acrobat 2020?) at which point free updates would stop. The key new feature you are interested in is "support for new systems". So, soon, there could be a new system and your Acrobat 2017 could be useless because there has been a newer Acrobat. You may consider it heresy, but a subscription also allows you to switch to Windows without buying again.
"Why would I want to pay a subscription of $15/month?"
Acrobat 2017 lists at around $440. That's almost 3 years' subscription. System changes are coming ever faster, with ever less consideration for people with old apps. That $440 would be a gamble that your Acrobat 2017 wasn't made obsolete in the next 3 years by some system upgrade you really want. Your life of over 9 years for Acrobat X doesn't seem likely to be repeated.