My personal take as someone who is about to start their first SaaS: I'll simply be flattered if someone deems my product worth copying.
50 people - heck even 10 - who think my product is worth using and I'm happy. That's how low my expectations are, just to keep myself sane :)
(I'm obv. not counting on this product making me a full-time income. I'm doing it for the experience and to get a feel for the industry.)
We'll see though, and you are right that keeping low expectations is a key.
Even thought articles like these (and all the comments here) can give a lot of (good?) information, it can also create a bunch of paralysis.
I'm also working on starting my first SaaS and I completely believe that "you don't learn until you launch".
That my product is copied and 90% of my user have been captured? WOW! I came up and built an idea worth copying and with such potential on the market!? Let's do it again!
I think this is also the freedom of no VC/investors asking for their ROI and an stable income. We can experiment, see what works and go from there. I'd also be flattered if my idea gets copied :-) I can learn from my competitor and grow even more!
Good luck on your project!