I wasn't really sure what the point of the game was but I see now that its purpose is to serve as a dungeon maker for your friends to play. Which I think is a neat idea in a sense, but having to find someone to play a dungeon you made isn't always gonna be an option for most people. So I played it solo. Which I guess kind of ruined the game for me lol. But I like the idea. I'm kind of dumb but I thought it was super cool how you're given the ability to place blocks and I'm not entirely sure how that even works in the first place. So good on you for pulling the wool over my eyes cause I have no idea how you did that and it's cool. My main issue with the "editor" side of things is that during those sections you're still interrupted by random encounters, making building dungeons a lot more frustrating and tedious for the player. Which, sure might be ignored if the dungeons were say, 3 rooms. But the amount of dungeon rooms you're given feels overkill. It makes the builder want to get the dungeon done as soon as possible lest they die and lose their progress or want to constantly save to not lose that said progress. I feel like the final boss dragged on a lot longer than I felt was necessary which might've been rectified if I built an actual dungeon and leveled up my heroes, but the process of building it seemed so slow with all the random encounters. And I understand the encounters are there for balancing purposes, because if the builder was given infinite resources they could build a dungeon that is extremely affective at killing the player. But process just feels so slow. Maybe have the builders have some alternative way of making money that doesn't feel so disruptive. I feel like this idea could be improved upon but it is definitely a start.
Honestly the reason I stuck through to the end of the game was the writing. I didn't expect to laugh at this game but a lot of the jokes were funny. Especially the conversation with the final boss. I feel like it wouldn't really make sense without prior context, or knowledge of what an Isekai is but I thought it was funny as hell how the Isekai'd main character is some perverted psycho who killed his cat. I feel like putting that writing into another project would benefit you. It's what kept me playing the most and I wished there was more of it. Take this whole review with a grain of salt considering I didn't really play it correctly but I feel like there are some great ideas in here that could use refining. Keep up the good work.
P.S. You might want to add descriptions to the items the player buys. By default items "Potion" "Magic Water" "Dispel Herb" and "Stimulant" do not have descriptions in the RPGmakerMV database.
If I didn't already know what they did I probably wouldn't have bought them.