Major issues with Bitcoin.

1. 50%+ of The Hashing Power is KYC'd aka Compromised.

2. The Devs are bought out by Big Bitcoin.

3. There's no Quantum Resistant Protocols being implemented, or adopted at large, within ~5 years or so old Bitcoins could be taken out of wallets.

4. High Fees

5. Transaction uncertainty (some transactions are put into limbo even when paying high Sat/vB)

6. Many more but some have become less relevant now, some are hypothetical, we'll see as everything moves forward.