As someone who has played elden ring , dark souls and sekiro on my potato rig I can say sekiro is the easiest in the fromsoft line up . 

Now you might be wondering how the hell I played elden ring in my potato laptop which have 8 gb ram and integrated graphics well I am not gonna go deep I will keep it short I just downloaded a mod frn nexus mods called low texture. Which basically removes grass , reduce lod, rain and reduce texture and played the game in 800x450 . So that's it . On to the main topic 

Yes I think sekiro is the easiest in my opinion in this line up .why I think so ? Because you only need to master one basic parry system and that's all you are good to go . 

Genichiro and lady butterfly are really good tutorial bosses for you to master your parry because after that it's all a game about patience just like others.  Learn and parry master you are good and you can chomp all the bosses they do not have the wide attacking window . 

Dark souls 1-2 on the other hand are really slow for player while the movement of bosses are fast , wide and they hit pretty hard . Artorias , orenstein and smough , manus , sir alonne , smelter demon , ivory king . These bosses are some of the best from this game and they are harder as each boss has a different attacking window , different style to fight so you have to adjust to them in every manor like your rolling , the timing of your attack and all.  

Dark souls 3-4 the combat is more faster and more refined in boss battle . It doesn't matter if you are like " oh I defeated abyss watchers in 10 tries boom 100+ tries on gael , nameless king and midir" . 

Radahn , malenia , promised consort radahn , morgott , malikath . Each boss is designed to be fight in very different way . You have to study their patten so you can mix it with your rolling and attacking. 

Wolf basically can parry everything in sekiro and it's not even that difficult like you just need to master the timing of that parry and you are good to go . 

The reason why I made this post is because I am tired of seeing all those Indian gamers who rant on in every comment section when someone is playing a soulslike they will write "sekiro💀"  and show superior complex . 

(My personal take) sekiro is the easiest in fromsoft souls lineup