"I'm not that sort of person"

Somewhere behind all of this there's a picture of who you are. You're reserved. You don't gush. People who know you would say you're steady, private, not one for big declarations, and you're comfortable with that. The people who say the good thing out loud are a different type, warmer and louder and a bit embarrassing, and if you started doing it you'd be putting on a costume.

I think there are two things tangled up here, and only one of them is you. Reserve is a style. It's how much you say, how loudly, how often, and how much of yourself you put in the room. That's yours and I'm not asking you to change it. Silence about what you admire is a habit, and a habit isn't a personality. It's a thing you've done so many times that it's stopped feeling like a choice. The two got confused because they happen in the same body, but plenty of reserved people say the good thing, and they say it in a reserved way.

Picture it. A quiet person, the sort who speaks once in a meeting, turns to the colleague afterwards and says "those slides were the clearest we've had this year", and goes back to their desk. No warmth in the voice beyond the words. No follow-up. That's not gushing. If anything it carries more weight than the same words from the person who says it about everything, because everyone in the room knows this person doesn't say things they don't mean.

That, I'd argue, is the reserved person's advantage, and the drawer is throwing it away. Your good opinion is rare currency. When you do say it, it's believed at once, precisely because you're not that sort of person. The habit has taken the one thing your reserve is good for and made sure nobody gets it.

There's also a quieter question, which is whether "not that sort of person" is describing you or protecting you. I don't know the answer for you. I'd only point out that it's a very convenient trait to have, because it excuses you from every awkward moment in advance, and traits that convenient are worth a second look. If it's really who you are, the plain version of saying it, one sentence, no performance, will feel fine. If the plain version still feels impossible, it probably wasn't the style that was stopping you.

This is my reading, not a finding. But I've never seen a reserved person made ridiculous by one accurate sentence about someone else, and I've seen plenty of drawers that stayed shut in the name of a personality that would have survived opening them.