What is the impact of Jimi Hendrix on modern day guitarists like John Mayer and Eric Johnson?

Huge. Hendrix influenced virtually every guitarist past and present.

https://faroutmagazine.co.uk/why-stevie-ray-vaughan-loved-jimi-hendrix/https://www.thethings.com/john-mayer-shares-a-piece-he-wrote-for-50th-anniversary-of-jimi-hendrixs-death/

Both SRV and Mayer were massive fans of Hendrix. SRV covered both Hendrix’s Little Wing and Voodoo Child and Mayer has covered Wait until Tomorrow, Wind Cries Mary and Bold as Love.

https://www.musicradar.com/news/guitars/eric-johnson-what-jimi-hendrix-means-to-me-277346

EJ was also very influenced by Hendrix.

https://www.musicradar.com/news/guitars/steve-vai-what-jimi-hendrix-means-to-me-278147

So was Steve Vai.

https://guitar.com/news/music-news/joe-satriani-guitar-heroes-jimi-hendrix-number-one-pete-townshend/

and Joe Satriani.

https://bravewords.com/news/yngwie-malmsteen-memories-of-hendrix

and Yngwie Malmsteen.

https://faroutmagazine.co.uk/slash-named-his-favourite-jimi-hendrix-songs/

and Slash.

https://faroutmagazine.co.uk/john-frusciante-explains-why-jimi-hendrix-is-the-greatest-guitarist-of-all-time/

and John Frusciante.

https://www.musicradar.com/news/guitars/jimi-hendrix-week-joe-bonamassa-on-the-legends-influence-177740

and Joe Bonamassa

http://rockandrollgarage.com/the-2-jimi-hendrix-songs-joe-perry-said-are-some-of-his-favorites/

and Joe Perry.

https://www.discogs.com/master/166204-Paul-Gilbert-Tribute-To-Jimi-Hendrix

Paul Gilbert did an entire CD covering Hendrix.

http://rockandrollgarage.com/david-gilmour-opinion-on-jimi-hendrix/

and David Gilmour.

https://www.loudersound.com/features/brian-may-i-paid-a-thousand-pounds-for-jimi-hendrix

Brian May even paid for him to play at his university

https://faroutmagazine.co.uk/eric-clapton-jimi-hendrix-friendship/

Hendrix and Clapton were influenced by each other. It’s notable that Clapton changed to using Stratocasters almost exclusively after Hendrix’s death

https://rockcelebrities.net/jimmy-pages-confession-about-jimi-hendrix/

Jimmy page had high opinions about Hendrix too.

https://faroutmagazine.co.uk/jeff-beck-and-the-special-impact-jimi-hendrix-had-on-him/

same with Jeff Beck.

https://faroutmagazine.co.uk/ritchie-blackmore-on-jimi-hendrix-and-stevie-ray-vaughan/

Ritchie Blackmore said Hendrix inspired him.

https://ultimateclassicrock.com/billy-gibbons-jimi-hendrix-forum/

Billy Gibbons was floored by him

https://www.ultimate-guitar.com/news/general_music_news/kenny_wayne_shepherd_explains_why_hes_been_ending_each_show_for_almost_30_years_with_hendrix_classic_talks_success_of_blue_on_black.html

and Kenny Wayne Shepherd.

http://rockandrollgarage.com/how-keith-richards-reacted-when-he-first-saw-jimi-hendrix-playing/#:~:text=In%20an%20interview%20with%20San,%E2%80%93%20almost%20inadvertently%20ruined%20guitar.%E2%80%9D

Keith Richards was astonished by Hendrix.

https://faroutmagazine.co.uk/pete-townshend-on-his-strange-relationship-with-jimi-hendrix/

Pete Townshend said both he and Clapton were in awe of Hendrix like schoolboys

I think the only guitarist I know that definitively did his own thing separate from Hendrix was Eddie Van Halen:

https://www.vhnd.com/2009/03/17/eddie-van-halen-dismisses-jimi-hendrix-comparisons/