I've always felt that Oneplus is a brand that I should like on principle of having clean software with barebones but powerful hardware, but in reality, every single Oneplus phone I've seen always had some sort of big BUTs attached to them, so buying Oneplus always feels like settling.
Take the Oneplus One for example, that sandstone textured cover was THE most creative material I felt a phone could have had, and I'm honestly shocked nobody has ever done it again. But along with that of course, comes with the cringy "smash your phone" marketing campaign, the half-hearted attempt to distance themselves from their parent company Oppo, the whole software mess with CyanogenMod/OxygenOS, etc.
Had a Oneplus 3T for a while, same deal: Great phone when it works as intended, but they raised their price without making the phone better, and the inexplicable random restarts/battery drain is so irritating, never had another phone that does that.
Recently they've dropped all pretense of not being Oppo and abandoned their core audience, choosing to have the "courage" to drop the headphone jack. Mediocre Chinese phones with flagship specs are a dime a dozen, I just don't see a reason to buy them anymore.
I've had the 3t for a couple of years until the 6t came out and I'm still using that to this day. I've been happy with both of them, the 6t still works well and although e.g. the camera isn't the greatest I have no intention of getting another phone until this one is completely dead.
That said, I wouldn't buy a newer models since the pricing policy and the move away from their former principles made them a mediocre phone amongst many and I would definitely get a Pixel next if I had to.