I forgot to post about your updated file: 147MB is much more acceptable than 1.1GB.

A couple of things that I noticed from the very first area of the first map:

128 tall doors and over-used of FLAT20 on the floor. (FLAT20 is generally best used in small doses as a detail texture or whatever.)
Given that this is the very opening of your map, bot of these create a bit of an amateurish feel. First impressions count and all that.
A very quick edit makes that first area look like this:

I'm not saying that it's perfect, but it looks better - no?
It's also worth switching on developer mode in GZDoom (type developer 2 at the console). Doing this gives some potentially useful feedback about things that you might want to address:
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Skipped empty sprite CUPS (lump 336)
Skipped empty sprite SINNER (lump 337)
Skipped empty sprite SINNER (lump 405)
Skipped empty sprite KICK (lump 406)
Skipped empty sprite KICK (lump 414)
Skipped empty sprite BOOK (lump 415)
Skipped empty sprite BOOK (lump 425)
Skipped empty sprite HITLER (lump 426)
Skipped empty sprite HITLER (lump 552)
Skipped empty sprite HOWITZER (lump 553)
Skipped empty sprite HOWITZER (lump 599)
Skipped empty sprite MP (lump 600)
Skipped empty sprite MP (lump 605)
Skipped empty sprite MEGA (lump 606)
Skipped empty sprite MEGA (lump 628)
Skipped empty sprite POWERS (lump 629)
Skipped empty sprite POWERS (lump 664)
Skipped empty sprite FLESH (lump 733)
Skipped empty sprite FLESH (lump 790)
Skipped empty sprite ROTTER (lump 791)
Skipped empty sprite ROTTER (lump 828)
Skipped empty sprite PROPS (lump 839)
Skipped empty sprite PROPS (lump 875)
Skipped empty sprite CHAIR (lump 876)
Skipped empty sprite CHAIR (lump 885)
Skipped empty sprite GAAPKING (lump 886)
...
Invalid data encountered for texture Project E.N.T.R.Y. DEMO.wad:CREDITS
Resolved self-referencing texture by picking an older entry for TNT
Resolved self-referencing texture by picking an older entry for TECHTE01
Resolved self-referencing texture by picking an older entry for TECHTE02
Resolved self-referencing texture by picking an older entry for TECHTE03
Resolved self-referencing texture by picking an older entry for TECHTE04
Resolved self-referencing texture by picking an older entry for ARMORY
Resolved self-referencing texture by picking an older entry for STC03
...
Script warning, "Project E.N.T.R.Y. DEMO.wad:DECORATE" line 129:
Unknown class name '' of type 'BasicArmorBonus'
Script warning, "Project E.N.T.R.Y. DEMO.wad:DECORATE" line 132:
Unknown class name '' of type 'BasicArmorBonus'
Script warning, "Project E.N.T.R.Y. DEMO.wad:DECORATE" line 144:
Unknown class name '' of type 'BasicArmorBonus'
Script warning, "Project E.N.T.R.Y. DEMO.wad:DECORATE" line 147:
Unknown class name '' of type 'BasicArmorBonus'
Script warning, "Project E.N.T.R.Y. DEMO.wad:DECORATE" line 150:
Truncation of floating point constant 2.400000
Script warning, "Project E.N.T.R.Y. DEMO.wad:DECORATE" line 150:
Truncation of floating point constant 2.600000
and on starting map01, this also appears at the console.
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MAP01 - City Control
Line 1019 (type 70:Teleport), arg 4 is 1 (should be 0)
Map07
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MAP07 - Deception
Line 9333's right edge is unconnected
None of these things are game stoppers, but they do detract from the overall impression of the mod.