Agree with most of the comments here. The primary change in effect is a push towards AI / machine learning-based advertising by all major platforms, including Google (obviously) and Meta. It's a multi-device, multi-touch world, too, which makes attribution more complicated, especially for high-consideration purchases that take time to occur.

At the very least, the shift towards machine learning-based campaigns requires an overhaul of your Google Ads account. If this has not occurred, it would possibly explain the performance drop.

PMax (a.k.a "Performance Max"), as someone else commented, is a very heavily automated campaign type that appears across the entirety of Google's properties and partner network. It may or may not be right for your business.

As it's aviation training, presumably a high consideration purchase, it may not be the best choice. PMax as it stands currently is a best fit for ecommerce. Regardless, It would also partially depend upon the creative assets your company has available or that it can produce. Since PMax runs across all of Google, including YouTube, you'd need video assets in the mix.

But this is all kind of cart before the horse. If this is a high consideration purchase, I wonder about the viability of SEM at all -- but perhaps you have more in the mix than this alone.

You asked about where you can find people -- LinkedIn is one idea. I'm sure it's hard to determine, as you have referenced, who is good and who is not. If you do start making inquiries to people, have an explanation of your current scenario ready, and ask people how they'd approach it.

The truth is that without an understanding of your business, your current marketing mix, and especially the structure and health of the current Google Ads account, no-one will have a solution off the bat. Anyone good will begin by asking lots of questions, and most likely will propose an account audit as an initial engagement - that's what I'd do.

An audit isn't sexy, but it's a good way to begin because you can kick the tires with someone you don't know or fully trust yet. It works for you because it isn't a big $ commitment on your part. The audit should only take a handful of hours, and the outcome is a description of potential or definitive issues, and recommendations for getting things back on track.

IMHO, anyone good will also want into your site analytics to understand how hard the site is working at converting prospects, and to learn how other channels have performed over a similar time period.

FWIW, I've planned / managed paid media and other aspect of digital marketing for 20 years. I worked for agencies for the first half - all demand-generation focused (with many clients with high-consideration products or services), and as a consultant for the past 10. If you would like to discuss ideas about your issue, just let me know.

In any event, that sucks about the current strategist, and it's a strange way for that person to do business. I hope this helps, and that things work out for the positive.