Optimising Mobile Site

Hi Tim.. for years I have benefited from good SEO and I like to dabble in amateur optimisations, but recently i've fallen from #2 in my chosen google search to #4 and now to the bottom of first page ( and falling ). 

It turns out my biggest drama is LCP and the problematic image is my website banner, which I have optimised as far as I possibly can within my skill base. 

My question is, I can add a little code perhaps speed up the offending image, but when I go to edit the html in a photo element, there is none.  Should I perhaps re-upload the image in a  text box which allows me to tweak html , or is that a dumb idea?

It's only on mobile I suffer, but apparently that's where it's at, and all the advice is to design my site for mobile.  I actually hate mobile for ordering photos, but that is where the world is at and my biggest stumbling block with clients too.  Any advice? 

Thankyou in advance!

This is something I'm very interested in too, and you are right about mobile being a much heavier weighting in search engine ranks than desktop.

I've been doing courses on html and php so I could start tweaking my way back to the top of the search engines, but I quickly realized that I would have to manually edit each page and any changes or updates wipe them out. 

I'm watching the version log waiting for optimizations to start hitting, but given how long the feature request thread is, I might start playing with a custom home page and perhaps one or two custom landing pages for my main services as you only need key pages to rank, not your entire site.

That way I'm not messing with any of Sytist's code, and I can try make those pages rank as efficiently as possible without breaking anything. Biggest draw back is keeping those custom pages in line with the rest of the site which would always be a big manual effort (navigation, links etc).

It's such a lot of work isn't it?  It used to be that you could write some content and buzz some keywords and blam!  Now you have to manually optimise every page, every pic, every keyword.  Because of sudden and unexpected fall from grace, it made me realise how much things have changed lately O_O  .. nice to know im not the only one :)