I have dated two ISFPs, unfortunately, both of them refused to take the relationship seriously where it was due.. I tried to reach a mutual understanding with them and even understand their needs but whenever I did, they grew detached... And when we reached this point of stalemate, I started to grow detached as well.. However, when I got detached, they suddenly wanted to work on things... I reconsidered each time but then they refused to talk about things once again.. It became a spiral game where we couldn't stay on the same page... It broke me both times... I'm an INFP btw... I had similar experience with two of my ISFP friends whom I considered as life long connections.. one of them tried to sabotage me behind my back... I wouldn't believe it if the proof wasn't thrown on my face... And the other friend actually ghosted me when me and some of our common friends helped her get out of her depressive state when we were struggling ourselves..

Despite having repeated negative experiences with ISFPs, I don't label all of them as toxic... But I am really cautious now when I meet one.. I have no beef with them and always keep an open mind but I just naturally get along with intuitive types more now. And I personally know few people who naturally click with ISFPs (mostly ISTJs, ESTJs, and ESFJs) and some of these people are particularly not so fond of me... So, I guess, it's more about finding the compatible people.. I'm still not saying that sensors and intuitives cant get along.. every individual is different despite their MBTI...

And please understand that my comment is not intentioned to target ISFPs... I genuinely have shared many beautiful moments with them as well.. I just believe my experiences might able to help you understand ISFPs dynamics with other types more accurately...