The Gewerbeanmeldung typically registers you as a sole proprietor (Einzelunternehmer) or GbR (partnership). Most tech startups need a limited liability structure like GmbH (similar to LLC) or UG. Those require notarized founding documents, minimum capital requirements (€25,000 for GmbH), and a commercial register entry (Handelsregister)
The simple Gewerbeanmeldung structure is problematic for venture capital because most VCs require a corporate entity structure (GmbH/UG) and converting from a simple structure to a proper corporation later can trigger tax consequences.
At each investment round all shareholders must appear before a notary or provide notarized power of attorney, the entire investment agreement must be read aloud by the notary, changes to company documents require notarization, and each notarization costs thousands of euros and creates delays.
Major decisions which are likely to affect shareholders require formal shareholder meetings with proper notice periods. Unanimous consent is often required for key decisions. Capital increases must be executed through complex formal processes. Registration with the commercial register takes weeks. Minimum nominal values of shares restrict flexibility. Required reporting to tax authorities is extensive. I can go on and on. And don't even get me started about German employee stock option plans.