I 'fired' my last client over a decade ago, however, despite all the web changes since then human behaviour hasn't changed.
First a slight detour:
When first meeting with a new client I always asked (albeit not so bluntly):
* what do you want/expect?
* in what time frame?
* for what budget?
Which eliminated well over half quickly and cheaply. Following which one could have serious conversations on a variety of issues including (1) what SEO really is (and isn't) and (2) how long it actually takes, given current niche competition, to see results.
While generally new clients can be educated once the topic becomes Google specific it is often more akin to cult deprogramming.
Note: I'm sure you've seen the pushback from webdevs here on WebmasterWorld at the same time as they claim no longer being properly appreciated. Clients have much less exposure to problems and changes so more likely to resist as contradictory to accepted narrative.
If I was speaking to clients currently I'd use privacy as the wedge. I'd speak to:
* Google as ad network using search as a means to sell advertising.
* I'd mention the change in advertising from based on query and page topic to personalised and retargeted based on previous behaviours.
* which segues into how that is accomplished with tracking, beacons, etc.
* from which follows render time and associated irritations, which client can likely appreciate.
* I'd then describe the revolt against impressions; how Google had been hustling advertisers for a deacgde and how little since has actually changed. Except that enterprise advertisers are wary around Google and many have gone elsewhere.
* which flows into the number of bots a site sees daily, many referred from Google; how bot networks can affect CTR and in turn force claw back on revenue.
If they are still listening (if not good bye I can't afford you) I'd turn to Google's morphing from SE to portal; the take over of up to the top 4-results positions by ads, local 3-packs, knowledge and answer boxes, carousels, etc. all designed to answer directly and/or retain visitor with referring outside Google enterprises a last choice increasingly a remnant of an older system ŗ la tonsils or appendix.
And lastly I'd mention web growth and accompanying competition. There are simply many more than last year and every year prior making business viability increasingly difficult. Depending on niche and available investment.
If still listening then I'd get into goodroi's points of the interconnectedness of online marketing, indeed of offline as well. I hate to waste time because it may include unrecoverable costs, smaller clients are less amenable to educational time being billable, so the sooner with the bad news hot buttons the better.
Of course much depends on the client, their niche, and their requirements; which are needs, which wants, which desires and how terribly they cling to each.
getting back to the original question, how do you explain this climate? iíve run out of explanations that are client acceptable. You got to know when to hold 'em, know when to fold 'em
Know when to walk away and know when to run
---The Gambler by Don Schlitz