What are the disadvantages of IOTA?

Could you please elaborate on the disadvantages associated with IOTA? I'm particularly interested in understanding its scalability issues, security vulnerabilities, and any challenges it faces in terms of adoption and usability. Additionally, are there any concerns regarding its centralization tendencies or the reliability of its distributed ledger technology? I'd appreciate a detailed analysis of these potential drawbacks to help me make an informed decision about investing in IOTA.