As an INTJ 9, let me point out which parts of being a 9 are "cruft" from being conflated with INFJ, ISFJ, ISFP, INFP, etc.
Well then I don't let my emotions work on me then.

But I would agree with that.
I'm taking this from a site (I hope it may help those who are deciding on 9)
:
1. I often feel in union with nature and people. <- True, sometimes more with nature than people sometimes.
I don't.
2. Making choices can be very difficult. I can see the advantages and disadvantages of every option. <-True, true.
Most choices are easy for me. Choices dealing with intimate relationships is much more difficult.
3. It is sometimes hard for me to know what I want when I’m with other people. <- I don't know actually. lol
I know exactly what I want. The hard part was realizing that what I really wanted wasn't what I thought I wanted.
4. Others see me as peaceful, but inside I often feel anxious. <- I think people definitely KNOW when I'm anxious and that makes more of an F (because of Fe instead of Fi), they start walking further away from me.
People see me as competent, but inside I often feel anxious.
5. Instead of tackling what I really need to do, I sometimes do little, unimportant things. <- Lol like.. right now?
Me, too.
Fortunately, I've lucked out so much on the "competence" scale, I can goof off a lot and still get a lot more done than most other people in my position.
Also, the ability to goof off appears to be essential to staying sane and maintaining quality. If I focused on just getting things "done", I'd not have spent the time just thinking about things and realizing that I'd missed something important.
6. When there is unpleasantness going on around me, I just try to think about something else for a while. <- Yeah
When there is unpleasantness going on around me, I tell them to go away.
If they don't go away, then my "w8" comes out. I do not suffer bullies gladly. Especially as an INTJ.
7. I usually prefer walking away from a disagreement to confronting someone. <-Yes and no, it alternates.
Yes. Only the most important disagreements get my attention. Not because I fear the confrontation, but because I've learned to read when someone simply won't be convinced. If they won't be convinced, AND it is important, then I escalate things such that the person who won't be convinced is no longer a problem.
8. If I don’t have some routine and structure to my day, I get almost nothing done. <- Maybe? Seems correct.
This contradicts the fact that many ISFPs and INFPs identify as type 9. This may be the ISFJ/INFJ side.
As an INTJ, I don't need "routine and structure" to get things done. I just do them. Why do people need a song and dance to get things done?
9. I tend to put things off until the last minute, but I almost always get them done. <-Lol yup
Almost always true, but not the things having to do with my primary responsibilities for my job. It's more along the lines of, if there is something that I really don't want to do (because it is annoying/unpleasant, such as filling out paperwork) then I'll put it off.
10. I like to be calm and unhurried, but sometimes I overextend myself. <- Yes
I rarely overextend myself. I know what I'm capable of, and I will tell people point blank when their expectations of me are unrealistic.
11. When people try to tell me what to do or try to control me, I get stubborn. <-Oh ho yes.
It depends. If they tell me to do what I was going to do anyway, I just do it. If they tell me to do something and it isn't a huge deal, I do it. If they start bullying me, my "w8" comes out. As an INTJ, I don't let people micromanage me.
12. I like to be sure to have time in my day for relaxing. <- Like a necessity, almost.
This is the case for all introverts, and almost all type 9s are introverts.
13. Sometimes I feel shy and unsure of myself. <- Yes, but that's from absorption of others emotions too.
*sigh* INTROVERTS.
IN
TRO
VERTS
*sigh*
This isn't a "type 9" thing.
14. I enjoy just hanging out with my partner or friends. <- Yes. Idk how this couldn't happen in other types as well?
No one I know enjoys just hanging out with their partner or friends.
15. Supportive and harmonious relationships are very important to me. <- Definitely.
Meh.
Relationships that involve an actual connection with the other person are important to me. Supportive and harmonious are secondary attributes, at best.
16. I am very sensitive about being judged and take criticism personally. <- Very so.
INTJs don't do that shit. And those that do pretend that they don't.
17. I like to listen and give people support. <- Mhm. Sometimes. Lol.
Most of the time, for me, actually. INTJs love to be experts and pontificate about their expertise. It SOUNDS arrogant and self-important, but it's the INTJ way of helping people. That's why we end up in high-end technical consulting jobs, because that's about the only arena in which one can get away with being helpful AND sounding arrogant and self-important.
18. I focus more on the positive than on the negative. <-I try to.
Mostly. The lesson for 9s is to focus on the negative to see what we can learn from it.
19. I have trouble getting rid of things. <- Lol.. yeah but I then going into all out streaks of like elimination of pointless stuff.
Um, no. I'm lazy about getting rid of things, but when push comes to shove, poof, they're gone.
20. I operate under the principle of inertia: If I’m going, it’s easy to keep going, but I sometimes have a hard time getting started. <- Wow. Yeah.
This one is pretty true for me, too. In a weird way, that makes things easy. Decide to start and then start, and THEN it's easy after that.
Anyway, I hope this helps ...