I think the Death March webnovel is the best truly conventional isekai out there. It scratches any itch you would want from a self insert fantasy isekai: crafting swords of great power, magic mecha's, inventing spells, a harem that contains essentially every type (except trap), drinking and feasting with dwarves, hanging out in a secluded elf village, standard genre aware comedy, some mystery and intrigue and characters deep enough that they come across as alive without the story becoming any less fast food-entertainmenty. It does not push the envelope but that is the beauty of it. It hits every cliche , and these things are cliche for a reason: because they are enjoyable. Along with an MC who is neither a bleeding heart nor a psychopath (though if you just watch the anime he seems bleeding heart) and has the maturity that comes with his age (rather than acting like an awkward horny teenager) it will give you the perfect isekai fantasy experience. Anything anyone would argue is better breaks the conventions somehow (Overlord (Montrous protag and lots of other stuff), No Game No Life (No fighting) etc) but I assure you no webnovel that directly follows the conventions comes close in entertainment value. If someone wants the best true isekai experience I will point directly at Death March.