tl;dr: Upgrades too rng instead of shaped to your desired playstile; does not value your time investment; makes final/synergy upgrades not very transparent initially; tedious af. Could be good if this were fixed.

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Could be a top tier Vampire-Survivors-Like roguelike, but the usual genre BS is hampering decent fun playtime.
Why?
There is no banish, rerolls are VERY limited and unless you really get a specific synergy build going with the mech you are using, you will simply invest 10-20 minutes into certain failure, because the culmination of the map will simply overwhelm you unless you are sufficiently powered.
You would think an intelligent game design would exist with which the ranged mech only gets suggested ranged upgrades (or at the VERY FRICKIN LEAST there is an option to do so or pre-select available upgrades for the map, or SOMETHING) and the blade based mech mainly gets the blade related main upgrades, and so on. But no. You might simply in the middle of a map run out of rerolls, get crappy non-synergy main weapons and then just plain lose and waste your time, as stated above.
Death must die has started to understand this dilemma and allowed skill trees, Swarm Grinder is still stuck in "must be roguelike and therefore peak annoying or I'm not a kewl roguelike" mode.
This is doubly sad, as this also prevents reaching upgrade path end-upgrades which boost specific styles even more.
If there were an option to narrow in on what kind of upgrade path you want to take (and, quite frankly, I would prefer doing this with either infinite rerolls and banishes or just plain with choosing my available upgrade options in advance without punishment) and a bit more sensible upgrade options in and of themselves (you have a "pacemaker" passive which supposedly helps with fuel consumption and survivability and then 2/3 of the options INCREASE fuel usage, yepp, that's right).

Anyway. Really fun the every 3rd to 5th time you manage to luck into your actually wanted build, horrendously tedious the rest of the time. Oh, and to add insult to injury? The meta upgrades have tiny steps like 2% faster movement, but costs like 2 completed runs, which, as stated above can mean 2 hours of pointless grind until you get there.
Fix these issues and you have a good game going.

tl;dr: Upgrades too rng instead of shaped to your desired playstile; does not value your time investment; makes final/synergy upgrades not very transparent initially; tedious af. Could be good if this were fixed. -- Could be a top tier Vampire-Survivors-Like roguelike, but the usual genre BS is hampering decent fun playtime. Why? There is no banish, rerolls are VERY limited and unless you really get a specific synergy build going with the mech you are using, you will simply invest 10-20 minutes into certain failure, because the culmination of the map will simply overwhelm you unless you are sufficiently powered. You would think an intelligent game design would exist with which the ranged mech only gets suggested ranged upgrades (or at the VERY FRICKIN LEAST there is an option to do so or pre-select available upgrades for the map, or SOMETHING) and the blade based mech mainly gets the blade related main upgrades, and so on. But no. You might simply in the middle of a map run out of rerolls, get crappy non-synergy main weapons and then just plain lose and waste your time, as stated above. Death must die has started to understand this dilemma and allowed skill trees, Swarm Grinder is still stuck in "must be roguelike and therefore peak annoying or I'm not a kewl roguelike" mode. This is doubly sad, as this also prevents reaching upgrade path end-upgrades which boost specific styles even more. If there were an option to narrow in on what kind of upgrade path you want to take (and, quite frankly, I would prefer doing this with either infinite rerolls and banishes or just plain with choosing my available upgrade options in advance without punishment) and a bit more sensible upgrade options in and of themselves (you have a "pacemaker" passive which supposedly helps with fuel consumption and survivability and then 2/3 of the options INCREASE fuel usage, yepp, that's right). Anyway. Really fun the every 3rd to 5th time you manage to luck into your actually wanted build, horrendously tedious the rest of the time. Oh, and to add insult to injury? The meta upgrades have tiny steps like 2% faster movement, but costs like 2 completed runs, which, as stated above can mean 2 hours of pointless grind until you get there. Fix these issues and you have a good game going.