How are you successfully switching jobs?

In case of referrals, getting referred by the hiring manager or a senior guy in the company like a director/H.O.E. is much better than getting referred by any random employee.

You can try this approach instead of applying via referrals/job portals. In linkedin, search "recruiter" and filter by company/location. You will get a list of recruiters. Send connection requests to them [ sometimes the follow button might be shown and the connection request button might be inside the profile ]. Whoever accepts, msg them. Your msg shoulf be the entire cover letter detailing your intro, your projects/exp and why would be fit for the company, and asking if there is any opening in the company. Your msg shouldn't be a small paragraph, instead it should be huge with multiple paras. Most likely, they wouldn't read the whole msg, but Do Make Sure that the msg is authentic and grammatically correct and it shouldn't look like an AI generated text. You can break the whole msg into 3-4 shorter msgs so that it appears that you have sent multiple msgs rather than 1 in the inbox. Like 1 msg for intro, 2nd msg for main stuff and 3rd msg for outro. Don't send the resume in that msg. If they reply, well and good, continue the convo. If they see the msg and not reply, try to follow up with a proper msg. You can send the resume in the 2nd or 3rd or even 4th msg. If they don't see the msg, do follow up but less frequently. Don't have high expectations. Assume only 1% or lesser conversion rate. Keeping sending invitation requests especially those companies which are hiring or those recruiters who have hiring in their dp.